Nature Chemical Biology2025. Wang, Qianwen et al.
Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
Nature Communications2025. TY Zhu et al.
Department of Medical Oncology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Life Science Institute, Zhejiang University, Hangzhou, Zhejiang, China
Journal of Chromatography A2025. H Zuo et al.
Key Laboratory of Resource Biology and Modern Biotechnology in Western China, College of Life Science, Northwest University, Xi'an 710069, PR China
Angewandte Chemie2024. Zhou, Mengya et al.
State Key Laboratory of Bioactive Molecules and Druggability Assessment, International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development (MOE), School of Pharmacy, Jinan University, 601 Huangpu Avenue West, 510632 Guangzhou, China
Journal of the American Chemical Society2024. Yue Liu et al.
State Key Laboratory of Bioactive Molecules and Druggability Assessment, Jinan University, 601 Huangpu Avenue West, Guangzhou 510632, China
Communications chemistry2024. Zhao, Yuanyuan et al.
State Key Laboratory of Bioactive Molecules and Druggability Assessment, Jinan University, 601 Huangpu Avenue West, Guangzhou, 510632, China
Biophysics Reports2023. Jian-Hua, Wang et al.
National Institute of Biological Sciences (NIBS), Beijing 102206, China
ABSTRACT:Transient and weak protein-protein interactions are essential to many biochemical reactions, yet are technically challenging to study. Chemical cross-linking of proteins coupled with mass spectrometry analysis (CXMS) provides a powerful tool in the analysis of such interactions. Central to this technology are chemical cross-linkers. Here, using two transient heterodimeric complexes EIN/HPr and EIIAGlc/EIIBGlc as our model systems, we evaluated the effects of two amine-specific homo-bifunctional cross-linkers with different reactivities. We showed previously that DOPA2 (di-ortho-phthalaldehyde with a di-ethylene glycol spacer arm) cross-links proteins 60-120 times faster than DSS (disuccinimidyl suberate). We found that though most of the intermolecular cross-links of either cross-linker are consistent with the encounter complexes (ECs), an ensemble of short-lived binding intermediates, more DOPA2 intermolecular cross-links could be assigned to the stereospecific complex (SC), the final lowest-energy conformational state for the two interacting proteins. Our finding suggests that faster cross-linking captures the SC more effectively and cross-linkers of different reactivities potentially probe protein-protein interaction dynamics across multiple timescales.
Redox Biology2023. Wu, Ting et al.
Center for Chemical Biology and Drug Discovery, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, 510530, China
ABSTRACT:Identifying direct substrates of enzymes has been a long-term challenge. Here, we present a strategy using live cell chemical cross-linking and mass spectrometry to identify the putative substrates of enzymes for further biochemical validation. Compared with other methods, our strategy is based on the identification of cross-linked peptides supported by high-quality MS/MS spectra, which eliminates false-positive discoveries of indirect binders. Additionally, cross-linking sites allow the analysis of interaction interfaces, providing further information for substrate validation. We demonstrated this strategy by identifying direct substrates of thioredoxin in both E. coli and HEK293T cells using two bis-vinyl sulfone chemical cross-linkers BVSB and PDES. We confirmed that BVSB and PDES have high specificity in cross-linking the active site of thioredoxin with its substrates both in vitro and in live cells. Applying live cell cross-linking, we identified 212 putative substrates of thioredoxin in E. coli and 299 putative S-nitrosylation (SNO) substrates of thioredoxin in HEK293T cells. In addition to thioredoxin, we have shown that this strategy can be applied to other proteins in the thioredoxin superfamily. Based on these results, we believe future development of cross-linking techniques will further advance cross-linking mass spectrometry in identifying substrates of other classes of enzymes.
Angewandte Chemie International Edition2023. Liu, Jialin et al.
College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking-Tsinghua Center for Life Sciences, Synthetic and Functional Biomolecules Center, and Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Peking University, Beijing, 100871 China
Proceedings of the National Academy of Sciences2023. de Kock, Willemien et al.
Groningen Institute of Archaeology, Faculty of Arts, University of Groningen, 9712 ER Groningen, Netherlands
Biochemistry2023. liuhaijun et al.
Department of Biology, Washington University in St. Louis, St. Louis, Missouri 63130, United States
ABSTRACT:Phycobilisomes (PBSs) are the major photosynthetic light-harvesting complexes in cyanobacteria and red algae. PBS, a multisubunit protein complex, has two major interfaces that comprise intrinsically disordered regions (IDRs): rod-core and core-membrane. IDRs do not form regular, three-dimensional structures on their own. Their presence in the photosynthetic pigment-protein complexes portends their structural and functional importance. A recent model suggests that PB-loop, an IDR located on the PBS subunit ApcE and C-terminal extension (CTE) of the PBS subunit ApcG, forms a structural protrusion on the PBS core-membrane side, facing the thylakoid membrane. Here, the structural synergy between the rod-core region and the core-membrane region was investigated using quantitative mass spectrometry (MS). The AlphaFold-predicted CpcG-CTE structure was first modeled onto the PBS rod-core region, guided and justified by the isotopically encoded structural MS data. Quantitative cross-linking MS analysis revealed that the structural proximity of the PB-loop in ApcE and ApcG-CTE is significantly disturbed in the absence of six PBS rods, which are attached to PBS via CpcG-CTE, indicative of drastic conformational changes and decreased structural integrity. These results suggest that CpcG-rod attachment on the PBS rod-core side is essentially required for the PBS core-membrane structural assembly. The hypothesized long-range synergy between the rod-core interface (where the orange carotenoid protein also functions) and the terminal energy emitter of PBS must have important regulatory roles in PBS core assembly, light-harvesting, and excitation energy transmission. These data also lend strategies that genetic truncation of the light-harvesting antennas aimed for improved photosynthetic productivity must rely on an in-depth understanding of their global structural integrity.
Life Science Alliance2022. Spittler, Didier et al.
Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY, USA
ABSTRACT:HIV-1 Rev mediates the nuclear export of intron-containing viral RNA transcripts and is essential for viral replication. Rev is imported into the nucleus by the host protein importin beta (Impbeta), but how Rev associates with Impbeta is poorly understood. Here, we report biochemical, mutational, and biophysical studies of the Impbeta/Rev complex. We show that Impbeta binds two Rev monomers through independent binding sites, in contrast to the 1:1 binding stoichiometry observed for most Impbeta cargos. Peptide scanning data and charge-reversal mutations identify the N-terminal tip of Rev helix alpha2 within Rev's arginine-rich motif (ARM) as a primary Impbeta-binding epitope. Cross-linking mass spectrometry and compensatory mutagenesis data combined with molecular docking simulations suggest a structural model in which one Rev monomer binds to the C-terminal half of Impbeta with Rev helix alpha2 roughly parallel to the HEAT-repeat superhelical axis, whereas the other monomer binds to the N-terminal half. These findings shed light on the molecular basis of Rev recognition by Impbeta and highlight an atypical binding behavior that distinguishes Rev from canonical cellular Impbeta cargos.
Life Science Alliance2022. Spittler, Didier et al.
Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY, USA
ABSTRACT:HIV-1 Rev mediates the nuclear export of intron-containing viral RNA transcripts and is essential for viral replication. Rev is imported into the nucleus by the host protein importin beta (Impbeta), but how Rev associates with Impbeta is poorly understood. Here, we report biochemical, mutational, and biophysical studies of the Impbeta/Rev complex. We show that Impbeta binds two Rev monomers through independent binding sites, in contrast to the 1:1 binding stoichiometry observed for most Impbeta cargos. Peptide scanning data and charge-reversal mutations identify the N-terminal tip of Rev helix alpha2 within Rev's arginine-rich motif (ARM) as a primary Impbeta-binding epitope. Cross-linking mass spectrometry and compensatory mutagenesis data combined with molecular docking simulations suggest a structural model in which one Rev monomer binds to the C-terminal half of Impbeta with Rev helix alpha2 roughly parallel to the HEAT-repeat superhelical axis, whereas the other monomer binds to the N-terminal half. These findings shed light on the molecular basis of Rev recognition by Impbeta and highlight an atypical binding behavior that distinguishes Rev from canonical cellular Impbeta cargos.
Proceedings of the National Academy of Sciences of the United States of America2022. Hart, Jonathan R et al.
Department of Molecular Medicine, Scripps Research Institute, La Jolla, CA 92037
ABSTRACT:Nanobodies and chemical cross-linking were used to gain information on the identity and positions of flexible domains of PI3Kalpha. The application of chemical cross-linking mass spectrometry (CXMS) facilitated the identification of the p85 domains BH, cSH2, and SH3 as well as their docking positions on the PI3Kalpha catalytic core. Binding of individual nanobodies to PI3Kalpha induced activation or inhibition of enzyme activity and caused conformational changes that could be correlated with enzyme function. Binding of nanobody Nb3-126 to the BH domain of p85alpha substantially improved resolution for parts of the PI3Kalpha complex, and binding of nanobody Nb3-159 induced a conformation of PI3Kalpha that is distinct from known PI3Kalpha structures. The analysis of CXMS data also provided mechanistic insights into the molecular underpinning of the flexibility of PI3Kalpha.
Proceedings of the National Academy of Sciences of the United States of America2022. Rahman, Sanim et al.
Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
Science Advances2022. Han, Wenyu et al.
State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai 200031,China
ABSTRACT:The cytoskeletal proteins tubulin and actin are the obligate substrates of TCP-1 ring complex/Chaperonin containing TCP-1 (TRiC/CCT), and their folding involves co-chaperone. Through cryo-electron microscopy analysis, we present a more complete picture of TRiC-assisted tubulin/actin folding along TRiC adenosine triphosphatase cycle, under the coordination of co-chaperone plp2. In the open S1/S2 states, plp2 and tubulin/actin engaged within opposite TRiC chambers. Notably, we captured an unprecedented TRiC-plp2-tubulin complex in the closed S3 state, engaged with a folded full-length beta-tubulin and loaded with a guanosine triphosphate, and a plp2 occupying opposite rings. Another closed S4 state revealed an actin in the intermediate folding state and a plp2. Accompanying TRiC ring closure, plp2 translocation could coordinate substrate translocation on the CCT6 hemisphere, facilitating substrate stabilization and folding. Our findings reveal the folding mechanism of the major cytoskeletal proteins tubulin/actin under the coordination of the biogenesis machinery TRiC and plp2 and extend our understanding of the links between cytoskeletal proteostasis and related human diseases.
ANALYTICAL AND BIOANALYTICAL CHEMISTRY2021. Gonz{\'a}lez, Luis Javier et al.
Animal Biotechnology Department, Center for Genetic Engineering and Biotechnology (CIGB), Avenida 31, e/ 158 y 190, Cubanacn, Playa, 10600 Havana, Cuba
ABSTRACT:A peptide from the P0 acidic ribosomal protein (pP0) of ticks conjugated to keyhole limpet hemocyanin from Megathura crenulata has shown to be effective against different tick species when used in host vaccination. Turning this peptide into a commercial anti-tick vaccine will depend on finding the appropriate, technically and economically feasible way to present it to the host immune system. Two conjugates (p64K-Cys(1)pP0 and p64K-beta Ala(1)pP0) were synthesized using the p64K carrier protein from Neisseria meningitidis produced in Escherichia coli, the same cross-linking reagent, and two analogues of pP0. The SDS-PAGE analysis of p64K-Cys(1)pP0 showed a heterogeneous conjugate compared to p64K-beta Ala(1)pP0 that was detected as a protein band at 91kDa. The pP0/p64K ratio determined by MALDI-MS for p64K-Cys(1)pP0 ranged from 1 to 8, being 3-5 the predominant ratio, while in the case of p64K-beta Ala(1)pP0 this ratio was 5-7. Cys(1)pP0 was partially linked to 35 out of 39 Lys residues and the N-terminal end, while beta Ala(1)pP0 was mostly linked to the six free cysteine residues, to the N-terminal end, and, in a lesser extent, to Lys residues. The assignment of the conjugation sites and side reactions were based on the identification of type 2 peptides. Rabbit immunizations showed the best anti-pP0 titers and the highest efficacy against Rhipicephalus sanguineus ticks when the p64K-Cys(1)pP0 was used as vaccine antigen. The presence of high molecular mass aggregates observed in the SDS-PAGE analysis of p64K-Cys(1)pP0 could be responsible for a better immune response against pP0 and consequently for its better efficacy as an anti-tick vaccine.
ANALYTICAL AND BIOANALYTICAL CHEMISTRY2021. Gonz{\'a}lez, Luis Javier et al.
Animal Biotechnology Department, Center for Genetic Engineering and Biotechnology (CIGB), Avenida 31, e/ 158 y 190, Cubanacn, Playa, 10600 Havana, Cuba
ABSTRACT:A peptide from the P0 acidic ribosomal protein (pP0) of ticks conjugated to keyhole limpet hemocyanin from Megathura crenulata has shown to be effective against different tick species when used in host vaccination. Turning this peptide into a commercial anti-tick vaccine will depend on finding the appropriate, technically and economically feasible way to present it to the host immune system. Two conjugates (p64K-Cys(1)pP0 and p64K-beta Ala(1)pP0) were synthesized using the p64K carrier protein from Neisseria meningitidis produced in Escherichia coli, the same cross-linking reagent, and two analogues of pP0. The SDS-PAGE analysis of p64K-Cys(1)pP0 showed a heterogeneous conjugate compared to p64K-beta Ala(1)pP0 that was detected as a protein band at 91kDa. The pP0/p64K ratio determined by MALDI-MS for p64K-Cys(1)pP0 ranged from 1 to 8, being 3-5 the predominant ratio, while in the case of p64K-beta Ala(1)pP0 this ratio was 5-7. Cys(1)pP0 was partially linked to 35 out of 39 Lys residues and the N-terminal end, while beta Ala(1)pP0 was mostly linked to the six free cysteine residues, to the N-terminal end, and, in a lesser extent, to Lys residues. The assignment of the conjugation sites and side reactions were based on the identification of type 2 peptides. Rabbit immunizations showed the best anti-pP0 titers and the highest efficacy against Rhipicephalus sanguineus ticks when the p64K-Cys(1)pP0 was used as vaccine antigen. The presence of high molecular mass aggregates observed in the SDS-PAGE analysis of p64K-Cys(1)pP0 could be responsible for a better immune response against pP0 and consequently for its better efficacy as an anti-tick vaccine.
Iscience2021. Yi, XP et al.
Baylor Coll Med, Lester & Sue Smith Breast Ctr, Houston, TX 77030 USA.
ABSTRACT:Comprehensive characterization of tumor antigens is essential for the design of cancer immunotherapies, and mass spectrometry (MS)-based immunopeptidomics enables high-throughput identification of major histocompatibility complex (MHC)-bound peptide antigens in vivo. Here we construct an immunopeptidome atlas of human cancer through an extensive collection of 43 published immunopeptidomic datasets and standardized analysis of 81.6 million MS/MS spectra using an open search engine. Our analysis greatly expands the current knowledge of MHC-bound antigens, including an unprecedented characterization of post-translationally modified antigens and their cancer-association. We also perform systematic analysis of cancer-testis antigens, cancer-associated antigens, and neoantigens. We make all these data together with annotated MS/MS spectra supporting identification of each antigen in an easily browsable web portal named cancer antigen atlas ( caAtlas). caAtlas provides a central resource for the selection and prioritization of MHC-bound peptides for in vitro HLA binding assay and immunogenicity testing, which will pave the way to eventual development of cancer immunotherapies.
JOURNAL OF IMMUNOLOGY2021. Yang, Naiqi et al.
Soochow Univ, Inst Biol, 199 Renai Rd, Suzhou 215123, Jiangsu, Peoples R China; Soochow Univ, Inst Med Sci, 199 Renai Rd, Suzhou 215123, Jiangsu, Peoples R China
ABSTRACT:Adhesion and degranulation-promoting adapter protein (ADAP), originally identified as an essential adaptor molecule in TCR signaling and T cell adhesion, has emerged as a critical regulator in innate immune cells such as macrophages; however, its role in macrophage polarization and inflammatory responses remains unknown. In this study, we show that ADAP plays an essential role in TLR4-mediated mouse macrophage polarization via modulation of STAT3 activity. Macrophages from ADAP-deficient mice exhibit enhanced M1 polarization, expression of proinflammatory cytokines and capacity in inducing Th1 responses, but decreased levels of anti-inflammatory cytokines in response to TLR4 activation by LPS. Furthermore, overexpression of ADAP enhances, whereas loss of ADAP reduces, the LPS-mediated phosphorylation and activity of STAT3, suggesting ADAP acts as a coactivator of STAT3 activity and function. Furthermore, the coactivator function of ADAP mostly depends on the tyrosine phosphorylation at Y571 in the motif YDSL induced by LPS. Mutation of Y571 to F severely impairs the stimulating effect of ADAP on STAT3 activity and the ability of ADAP to inhibit M1-like polarization in TLR4-activated mouse macrophages. Moreover, ADAP interacts with STAT3, and loss of ADAP renders mouse macrophages less sensitive to IL-6 stimulation for STAT3 phosphorylation. Collectively, our findings revealed an additional layer of regulation of TLR4-mediated mouse macrophage plasticity whereby ADAP phosphorylation on Y571 is required to prime STAT3 for activation in TLR4-stimulated mouse macrophages.
Nature Communications2021. Prince, JP et al.
Univ Oxford, Dept Biochem, South Parks Rd, Oxford OX1 3QU, England.
ABSTRACT:Structural Maintenance of Chromosomes (SMC) complexes act ubiquitously to compact DNA linearly, thereby facilitating chromosome organization-segregation. SMC proteins have a conserved architecture, with a dimerization hinge and an ATPase head domain separated by a long antiparallel intramolecular coiled-coil. Dimeric SMC proteins interact with essential accessory proteins, kleisins that bridge the two subunits of an SMC dimer, and HAWK/KITE proteins that interact with kleisins. The ATPase activity of the Escherichia coli SMC protein, MukB, which is essential for its in vivo function, requires its interaction with the dimeric kleisin, MukF that in turn interacts with the KITE protein, MukE. Here we demonstrate that, in addition, MukB interacts specifically with Acyl Carrier Protein (AcpP) that has essential functions in fatty acid synthesis. We characterize the AcpP interaction at the joint of the MukB coiled-coil and show that the interaction is necessary for MukB ATPase and for MukBEF function in vivo. E. coli MukBEF is an SMC complex that plays key roles in chromosome organization-segregation. Here the authors show that the interaction between MukBEF and the Acyl Carrier Protein (AcpP) is essential for MukBEF activity in vitro (ATPase) and in vivo.
Genomics, proteomics & bioinformatics2020. Lin, XH et al.
Chinese Acad Sci, Inst Hydrobiol, State Key Lab Freshwater Ecol & Biotechnol, Wuhan 430072, Peoples R China.
ABSTRACT:Protein lysine methylation is a prevalent post-translational modification (PTM) and plays critical roles in all domains of life. However, its extent and function in photosynthetic organisms are still largely unknown. Cyanobacteria are a large group of prokaryotes that carry out oxygenic photosynthesis and are applied extensively in studies of photosynthetic mechanisms and environmental adaptation. Here we integrated propionylation of monomethylated proteins, enrichment of the modified peptides, and mass spectrometry (MS) analysis to identify monomethylated proteins in Synechocystis sp. PCC 6803 (Synechocystis). Overall, we identified 376 monomethylation sites in 270 proteins, with numerous monomethylated proteins participating in photosynthesis and carbon metabolism. We subsequently demonstrated that CpcM, a previously identified asparagine methyl-transferase in Synechocystis, could catalyze lysine monomethylation of the potential aspartate amino-transferase 5110480 both in vivo and in vitro and regulate the enzyme activity of 5110480. The loss of CpcM led to decreases in the maximum quantum yield in primary photosystem II (PSII) and the efficiency of energy transfer during the photosynthetic reaction in Synechocystis. We report the first lysine monomethylome in a photosynthetic organism and present a critical database for functional analyses of monomethylation in cyanobacteria. The large number of monomethylated proteins and the identification of CpcM as the lysine methyltransferase in cyanobacteria suggest that reversible methylation may influence the metabolic process and photosynthesis in both cyanobacteria and plants.
Genomics, proteomics & bioinformatics2020. Lin, XH et al.
Chinese Acad Sci, Inst Hydrobiol, State Key Lab Freshwater Ecol & Biotechnol, Wuhan 430072, Peoples R China.
ABSTRACT:Protein lysine methylation is a prevalent post-translational modification (PTM) and plays critical roles in all domains of life. However, its extent and function in photosynthetic organisms are still largely unknown. Cyanobacteria are a large group of prokaryotes that carry out oxygenic photosynthesis and are applied extensively in studies of photosynthetic mechanisms and environmental adaptation. Here we integrated propionylation of monomethylated proteins, enrichment of the modified peptides, and mass spectrometry (MS) analysis to identify monomethylated proteins in Synechocystis sp. PCC 6803 (Synechocystis). Overall, we identified 376 monomethylation sites in 270 proteins, with numerous monomethylated proteins participating in photosynthesis and carbon metabolism. We subsequently demonstrated that CpcM, a previously identified asparagine methyl-transferase in Synechocystis, could catalyze lysine monomethylation of the potential aspartate amino-transferase 5110480 both in vivo and in vitro and regulate the enzyme activity of 5110480. The loss of CpcM led to decreases in the maximum quantum yield in primary photosystem II (PSII) and the efficiency of energy transfer during the photosynthetic reaction in Synechocystis. We report the first lysine monomethylome in a photosynthetic organism and present a critical database for functional analyses of monomethylation in cyanobacteria. The large number of monomethylated proteins and the identification of CpcM as the lysine methyltransferase in cyanobacteria suggest that reversible methylation may influence the metabolic process and photosynthesis in both cyanobacteria and plants.
Current bioinformatics2020. Rolfs, Z et al.
Univ Wisconsin, Dept Chem, 1101 Univ Ave, Madison, WI 53706 USA.
ABSTRACT:Background: The identification of non-specifically cleaved peptides in proteomics and peptidomics poses a significant computational challenge. Current strategies for the identification of such peptides are typically time-consuming and hinder routine data analysis. Objective: We aimed to design an algorithm that would improve the speed of semi- and nonspecific enzyme searches and could be applied to existing search programs. Methods: We developed a novel search algorithm that leverages fragment-ion redundancy to simultaneously search multiple non-specifically cleaved peptides at once. Briefly, a theoretical peptide tandem mass spectrum is generated using only the fragment-ion series from a single terminus. This spectrum serves as a proxy for several shorter theoretical peptides sharing the same terminus. After database searching, amino acids are removed from the opposing terminus until the observed and theoretical precursor masses match within a given mass tolerance. Results: The algorithm was implemented in the search program MetaMorpheus and found to perform an order of magnitude faster than the traditional MetaMorpheus search and produce superior results. Conclusion: We report a speedy non-specific enzyme search algorithm that is open-source and enables search programs to utilize fragmention redundancy to achieve a notable increase in search speed.
STAR Protocols2020. Li, Yi et al.
Peking University
ABSTRACT:Alk-Ph is a clickable APEX2 substrate developed for spatially restricted protein/RNA labeling in intact yeast cells. Alk-Ph is more water soluble and cell wall permeable than biotin-phenol substrate, allowing more efficient profiling of the subcellular proteome in microorganisms. We describe the protocol for Alk-Ph probe synthesis, APEX2 expression, and protein/RNA labeling in yeast and the workflow for quantitative proteomic experiments and data analysis. Using the yeast mitochondria as an example, we provide guidelines to achieve high-resolution mapping of subcellular yeast proteome and transcriptome. For complete details on the use and execution of this protocol, please refer to Li etal. (2020). 2020 The Author(s).
STAR Protocols2020. Li, Yi et al.
Peking University
ABSTRACT:Alk-Ph is a clickable APEX2 substrate developed for spatially restricted protein/RNA labeling in intact yeast cells. Alk-Ph is more water soluble and cell wall permeable than biotin-phenol substrate, allowing more efficient profiling of the subcellular proteome in microorganisms. We describe the protocol for Alk-Ph probe synthesis, APEX2 expression, and protein/RNA labeling in yeast and the workflow for quantitative proteomic experiments and data analysis. Using the yeast mitochondria as an example, we provide guidelines to achieve high-resolution mapping of subcellular yeast proteome and transcriptome. For complete details on the use and execution of this protocol, please refer to Li etal. (2020). 2020 The Author(s).
Journal of Proteomics2019. Ma, WT et al.
Hainan Univ, Inst Trop Agr & Forestry, Haikou 570228, Hainan, Peoples R China.
ABSTRACT:Peptide-spectrum matches (PSM) scoring between the experimental and theoretical spectrum is a key step in the identification of proteins using mass spectrometry (MS)-based proteomics analyses. Efficient protein identification using MS/MS data remains a challenge. The strategy of using RNA-seq data increases the number of proteins identified by re-constructing the custom search database and integrating mRNA abundance into the false discovery rate of post-PSM. However, this process lacks an algorithm that can allow the incorporation of mRNA abundance into the key scoring model of PSM. Therefore, we developed a novel PSM scoring model, which incorporates mRNA abundance for improved peptide and protein identification. In the new algorithm, abundance information of mRNA was transformed to the prior probability of protein identification and integrated to re-score in PSM using the binomial probability distribution model. Compared with other algorithms using five MS/MS datasets, the results showed that the least improvement ratios of peptide and protein groups were 3.39%-9.79% and 0.48%-8.16% in different datasets (human, rat, zebrafish, yeast, and Arabidopsis thaliana). The new strategy offers an effective solution for MS-based identification of peptides and proteins. Significance: The new algorithm identifies proteins by quantifying mRNA abundance (FPKM) and incorporating it into a scoring model for peptide-spectrum matches. It is important to improve peptide and protein identification from MS/MS datasets in proteomics research.
Genome research2019. Shao, Yi et al.
Chinese Acad Sci, State Key Lab Integrated Management Pest Insects, Inst Zool, Beijing 100101, Peoples R China; Chinese Acad Sci, CAS Ctr Excellence Anim Evolut & Genet, Kunming 650223, Yunnan, Peoples R China; Univ Chinese Acad Sci, Beijing 100049, Peoples R China; Chinese Acad Sci, Inst Zool, Key Lab Zool Systemat & Evolut, Beijing 100101, Peoples R China
ABSTRACT:The origination of new genes contributes to phenotypic evolution in humans. Two major challenges in the study of new genes are the inference of gene ages and annotation of their protein-coding potential. To tackle these challenges, we created GenTree, an integrated online database that compiles age inferences from three major methods together with functional genomic data for new genes. Genome-wide comparison of the age inference methods revealed that the synteny-based pipeline (SBP) is most suited for recently duplicated genes, whereas the protein-family-based methods are useful for ancient genes. For SBP-dated primate-specific protein-coding genes (PSGs), we performed manual evaluation based on published PSG lists and showed that SBP generated a conservative data set of PSGs by masking less reliable syntenic regions. After assessing the coding potential based on evolutionary constraint and peptide evidence from proteomic data, we curated a list of 254 PSGs with different levels of protein evidence. This list also includes 41 candidate misannotated pseudogenes that encode primate-specific short proteins. Coexpression analysis showed that PSGs are preferentially recruited into organs with rapidly evolving pathways such as spermatogenesis, immune response, mother-fetus interaction, and brain development. For brain development, primate-specific KRAB zinc-finger proteins (KZNFs) are specifically up-regulated in the mid-fetal stage, which may have contributed to the evolution of this critical stage. Altogether, hundreds of PSGs are either recruited to processes under strong selection pressure or to processes supporting an evolving novel organ.
MOLECULAR & CELLULAR PROTEOMICS2019. An, ZW et al.
Chinese Acad Sci, Acad Math & Syst Sci, Natl Ctr Math & Interdisciplinary Sci, Key Lab Random Complex Struct & Data Sci, Beijing 100190, Peoples R China.
ABSTRACT:The open (mass tolerant) search of tandem mass spectra of peptides shows great potential in the comprehensive detection of post-translational modifications (PTMs) in shotgun proteomics. However, this search strategy has not been widely used by the community, and one bottleneck of it is the lack of appropriate algorithms for automated and reliable post-processing of the coarse and error-prone search results. Here we present PTMiner, a software tool for confident filtering and localization of modifications (mass shifts) detected in an open search. After mass-shift-grouped false discovery rate (FDR) control of peptide-spectrum matches (PSMs), PTMiner uses an empirical Bayesian method to localize modifications through iterative learning of the prior probabilities of each type of modification occurring on different amino acids. The performance of PTMiner was evaluated on three data sets, including simulated data, chemically synthesized peptide library data and modified-peptide spiked-in proteome data. The results showed that PTMiner can effectively control the PSM FDR and accurately localize the modification sites. At 1% real false localization rate (FLR), PTMiner localized 93%, 84 and 83% of the modification sites in the three data sets, respectively, far higher than two open search engines we used and an extended version of the Ascore localization algorithm. We then used PTMiner to analyze a draft map of human proteome containing 25 million spectra from 30 tissues, and confidently identified over 1.7 million modified PSMs at 1% FDR and 1% FLR, which provided a system-wide view of both known and unknown PTMs in the human proteome.
BioMed Research International2018. An, Zhiwu et al.
State Key Laboratory of Bioactive Molecules and Druggability Assessment, International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development (MOE), School of Pharmacy, Jinan University, 601 Huangpu Avenue West, 510632 Guangzhou, China
ABSTRACT:Confident characterization of intact glycopeptides is a challenging task in mass spectrometry-based glycoproteomics due to microheterogeneity of glycosylation, complexity of glycans, and insufficient fragmentation of peptide bones. Open mass spectral library search is a promising computational approach to peptide identification, but its potential in the identification of glycopeptides has not been fully explored. Here we present pMatchGlyco, a new spectral library search tool for intact N-linked glycopeptide identification using high-energy collisional dissociation (HCD) tandem mass spectrometry (MS/MS) data. In pMatchGlyco, (1) MS/MS spectra of deglycopeptides are used to create spectral library, (2) MS/MS spectra of glycopeptides are matched to the spectra in library in an open (precursor tolerant) manner and the glycans are inferred, and (3) a false discovery rate is estimated for top-scored matches above a threshold. The efficiency and reliability of pMatchGlyco were demonstrated on a data set of mixture sample of six standard glycoproteins and a complex glycoprotein data set generated from human cancer cell line OVCAR3.
BioMed Research International2018. An, Zhiwu et al.
State Key Laboratory of Bioactive Molecules and Druggability Assessment, International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development (MOE), School of Pharmacy, Jinan University, 601 Huangpu Avenue West, 510632 Guangzhou, China
ABSTRACT:Confident characterization of intact glycopeptides is a challenging task in mass spectrometry-based glycoproteomics due to microheterogeneity of glycosylation, complexity of glycans, and insufficient fragmentation of peptide bones. Open mass spectral library search is a promising computational approach to peptide identification, but its potential in the identification of glycopeptides has not been fully explored. Here we present pMatchGlyco, a new spectral library search tool for intact N-linked glycopeptide identification using high-energy collisional dissociation (HCD) tandem mass spectrometry (MS/MS) data. In pMatchGlyco, (1) MS/MS spectra of deglycopeptides are used to create spectral library, (2) MS/MS spectra of glycopeptides are matched to the spectra in library in an open (precursor tolerant) manner and the glycans are inferred, and (3) a false discovery rate is estimated for top-scored matches above a threshold. The efficiency and reliability of pMatchGlyco were demonstrated on a data set of mixture sample of six standard glycoproteins and a complex glycoprotein data set generated from human cancer cell line OVCAR3.
Molecular cell2018. Zhan, Ni et al.
Chinese Acad Sci, Inst Genet & Dev Biol, CAS Ctr Excellence Mol Plant Sci, Beijing 100101, Peoples R China; Chinese Acad Sci, State Key Lab Plant Genom, Beijing 100101, Peoples R China; Univ Chinese Acad Sci, Beijing 100049, Peoples R China
ABSTRACT:Nitric oxide (NO) regulates diverse cellular signaling through S-nitrosylation of specific Cys residues of target proteins. The intracellular level of S-nitrosoglutathione (GSNO), a major bioactive NO species, is regulated by GSNO reductase (GSNOR), a highly conserved master regulator of NO signaling. However, little is known about how the activity of GSNOR is regulated. Here, we show that S-nitrosylation induces selective autophagy of Arabidopsis GSNOR1 during hypoxia responses. S-nitrosylation of GSNOR1 at Cys-10 induces conformational changes, exposing its AUTOPHAGY-RELATED8 (ATG8)-interacting motif (AIM) accessible by autophagy machinery. Upon binding by ATG8, GSNOR1 is recruited into the autophagosome and degraded in an AIM-dependent manner. Physiologically, the S-nitrosylation-induced selective autophagy of GSNOR1 is relevant to hypoxia responses. Our discovery reveals a unique mechanism by which S-nitrosylation mediates selective autophagy of GSNOR1, thereby establishing a molecular link between NO signaling and autophagy.
Journal of proteome research2018. Yang, Jing et al.
Wuhan Univ, Sch Pharmaceut Sci, Zhongnan Hosp, Wuhan 430071, Peoples R China; Tibet Univ, Coll Med, Lasa 850000, Peoples R China; Beijing Inst Life, Beijing Proteome Res Ctr, Natl Ctr Prot Sci Beijing, State Key Lab Prote, Beijing 102206, Peoples R China; Wuhan Univ, Sch Pharmaceut Sci, Key Lab Combinatorial Biosynth & Drug Discovery M, State Key Lab Virol, Wuhan 430071, Peoples R China; Wuhan Univ, Hubei Prov Key Lab Dev Originated Dis, Wuhan 430071, Peoples R China; Wuhan Univ, Sch Basic Med Sci, Hubei Prov Engn & Technol Res Ctr Fluorinated Pha, Ctr Expt Basic Med Educ, Wuhan 430071, Peoples R China; Anhui Med Univ, Hefei 230032, Anhui, Peoples R China
ABSTRACT:Targeted therapy of hepatocellular carcinoma (HCC) is essential for improved therapies. Therefore, identification of key targets specifically to HCC is an urgent requirement. Herein, an iTRAQ-quantitative proteomic approach was employed to identify differentially expressed proteins in HCC tumor tissues. Of the upregulated tumor-related proteins, minichromosome maintenance 2 (MCM2), a DNA replication licensing factor, was one of the most significantly altered proteins, and its over expression was confirmed using tissue microarray. Clinicopathological analysis of multiple cohorts of HCC patients indicated that overexpression of MCM2 was validated in 89.8% tumor tissues and strongly correlated with clinical stage. Furthermore, siRNA-mediated repression of MCM2 expression resulted in significant suppression of the HepG2 cell cycle and proliferation through the cyclin D-dependent kinases (CDKs) 2/7 pathway. Finally, the first small molecule-based MCM2-targeted NIR-II probe CH1055-MCM2 was concisely generated and subsequently evaluated in mice bearing HepG2 xenografts. The excellent imaging properties such as good tumor uptake and high tumor contrast and specificity were achieved in the small animal models. This analytical strategy can determine novel accessible targets of HCC useful for imaging and therapy.
Nature Chemical Biology2018. Akter, S et al.
Scripps Res Inst, Dept Chem, Jupiter, FL 33458 USA.
ABSTRACT:Cysteine sulfinic acid or S-sulfinylation is an oxidative post-translational modification (OxiPTM) that is known to be involved in redox-dependent regulation of protein function but has been historically difficult to analyze biochemically. To facilitate the detection of S-sulfinylated proteins, we demonstrate that a clickable, electrophilic diazene probe (DiaAlk) enables capture and site-centric proteomic analysis of this OxiPTM. Using this workflow, we revealed a striking difference between sulfenic acid modification (S-sulfenylation) and the S-sulfinylation dynamic response to oxidative stress, which is indicative of different roles for these OxiPTMs in redox regulation. We also identified >55 heretofore-unknown protein substrates of the cysteine sulfinic acid reductase sulfiredoxin, extending its function well beyond those of 2-cysteine peroxiredoxins (2-Cys PRDX1-4) and offering new insights into the role of this unique oxidoreductase as a central mediator of reactive oxygen species-associated diseases, particularly cancer. DiaAlk therefore provides a novel tool to profile S-sulfinylated proteins and study their regulatory mechanisms in cells.
Frontiers in plant science2017. Zhang, Yunxiang et al.
Chinese Acad Sci, Inst Mt Hazards & Environm, Key Lab Mt Surface Proc & Ecol Regulat, Chengdu, Peoples R China
ABSTRACT:With increasing altitude, solar UV-B radiation is enhanced. Based on the phenomenon of male-biased sex ratio of Populus cathayana Rehder in high altitude alpine area, we hypothesized that males have a faster and more sophisticated responsive mechanism to high UV-B radiation than that of females. Our previous studies have shown sexually different responses to high UV-B radiation were existed in P. cathayana at the morphological, physiological, and transcriptomic levels. However, the responses at the proteomic level remain unclear. In this study, an isobaric tag for relative and absolute quantification (iTRAQ)-based quantitative proteome analysis was performed in P. cathayana females and males. A total of 2,405 proteins were identified, with 331 proteins defined as differentially expressed proteins (DEPs). Among of these, 79 and 138 DEPs were decreased and 47 and 107 DEPs were increased under high solar UV-B radiation in females and males, respectively. A bioinformatics analysis categorized the common responsive proteins in the sexes as related to carbohydrate and energy metabolism, translation/transcription/post-transcriptional modification, photosynthesis, and redox reactions. The responsive proteins that showed differences in sex were mainly those involved in amino acid metabolism, stress response, and translation/transcription/post-transcriptional modification. This study provides proteomic profiles that poplars responding to solar UV-B radiation, and it also provides new insights into differentially sex-related responses to UV-B radiation.
Frontiers in plant science2017. Zhang, Yunxiang et al.
Chinese Acad Sci, Inst Mt Hazards & Environm, Key Lab Mt Surface Proc & Ecol Regulat, Chengdu, Peoples R China
ABSTRACT:With increasing altitude, solar UV-B radiation is enhanced. Based on the phenomenon of male-biased sex ratio of Populus cathayana Rehder in high altitude alpine area, we hypothesized that males have a faster and more sophisticated responsive mechanism to high UV-B radiation than that of females. Our previous studies have shown sexually different responses to high UV-B radiation were existed in P. cathayana at the morphological, physiological, and transcriptomic levels. However, the responses at the proteomic level remain unclear. In this study, an isobaric tag for relative and absolute quantification (iTRAQ)-based quantitative proteome analysis was performed in P. cathayana females and males. A total of 2,405 proteins were identified, with 331 proteins defined as differentially expressed proteins (DEPs). Among of these, 79 and 138 DEPs were decreased and 47 and 107 DEPs were increased under high solar UV-B radiation in females and males, respectively. A bioinformatics analysis categorized the common responsive proteins in the sexes as related to carbohydrate and energy metabolism, translation/transcription/post-transcriptional modification, photosynthesis, and redox reactions. The responsive proteins that showed differences in sex were mainly those involved in amino acid metabolism, stress response, and translation/transcription/post-transcriptional modification. This study provides proteomic profiles that poplars responding to solar UV-B radiation, and it also provides new insights into differentially sex-related responses to UV-B radiation.
Analytical chemistry2017. Zhao, Qun et al.
Chinese Acad Sci, Dalian Inst Chem Phys, Natl Chromatog R&A Ctr, Key Lab Separat Sci Analyt Chem, Dalian 116023, Peoples R China
ABSTRACT:Although great achievement has been made in the mapping of human proteome, the efficiency of sample preparation still needs to be improved, especially for membrane proteins. Herein, we presented a novel method to deepen proteome coverage by the sequential extraction of proteins using urea and 1-dodecy1-3- methylimidazolium chloride (C12Im-Cl). With such a strategy, the commonly lost hydrophobic proteins by 8 M urea extraction could be further recovered by C12Im-Cl, as well as the suppression effect of high abundance soluble proteins could be decreased. Followed by the in situ sample preparation and separation with different stationary phases, more than 9810 gene products could be identified, covering 8 orders of magnitude in abundance, which was, to the best of our knowledge, the largest data set of HeLa cell proteome. Compared with previous work, not only the number of proteins identified was obviously increased, but also the analysis time was shortened to a few days. Therefore, we expect that such a strategy has great potential applications to achieve unprecedented coverage for proteome analysis.
Nature Communications2017. Han, CF et al.
Ocean Univ China, Sch Med & Pharm, 5 Yushan Rd, Qingdao 266003, Peoples R China.
ABSTRACT:SIRT1 is the most evolutionarily conserved mammalian sirtuin, and it plays a vital role in the regulation of metabolism, stress responses, genome stability, and ageing. As a stress sensor, SIRT1 deacetylase activity is significantly increased during stresses, but the molecular mechanisms are not yet fully clear. Here, we show that SIRT1 is dynamically modified with O-GlcNAc at Ser 549 in its carboxy-terminal region, which directly increases its deacetylase activity both in vitro and in vivo. The O-GlcNAcylation of SIRT1 is elevated during genotoxic, oxidative, and metabolic stress stimuli in cellular and mouse models, thereby increasing SIRT1 deacetylase activity and protecting cells from stress-induced apoptosis. Our findings demonstrate a new mechanism for the activation of SIRT1 under stress conditions and suggest a novel potential therapeutic target for preventing age-related diseases and extending healthspan.
ABSTRACT:Malaria parasites modify their human host cell, the mature erythrocyte. This modification is mediated by a large number of parasite proteins that are exported to the host cell, and is also the underlying cause for the pathology caused by malaria infection. Amongst these proteins are many Hsp40 co-chaperones, and a single Hsp70. These proteins have been implicated in several processes in the host cell, including a potential role in protein transport, however the further molecular players in this process remain obscure. To address this, we have utilized chemical cross-linking followed by mass spectrometry and immunoblotting to isolate and characterize proteins complexes containing an exported Hsp40 (PFE55), and the only known exported Hsp70 (PfHsp70x). Our data reveal that both of these proteins are contained in high molecular weight protein complexes. These complexes are found both in the infected erythrocyte, and within the parasite-derived compartment referred to as the parasitophorous vacuole. Surprisingly, our data also reveal an association of PfHsp70x with components of PTEX, a putative protein translocon within the membrane of the parasitophorous vacuole. Our results suggest that the P. falciparum-infected human erythrocyte contains numerous high molecular weight protein complexes, which may potentially be involved in host cell modification.
Molecular & Cellular Poteomics2016. Olsen, JB et al.
Lilly USA, Lilly Res Labs, Indianapolis, IN 46285 USA.
ABSTRACT:The significance of non-histone lysine methylation in cell biology and human disease is an emerging area of research exploration. The development of small molecule inhibitors that selectively and potently target enzymes that catalyze the addition of methyl-groups to lysine residues, such as the protein lysine mono-methyltransferase SMYD2, is an active area of drug discovery. Critical to the accurate assessment of biological function is the ability to identify target enzyme substrates and to define enzyme substrate specificity within the context of the cell. Here, using stable isotopic labeling with amino acids in cell culture (SILAC) coupled with immunoaffinity enrichment of mono-methyl-lysine (Kme1) peptides and mass spectrometry, we report a comprehensive, large-scale proteomic study of lysine mono-methylation, comprising a total of 1032 Kme1 sites in esophageal squamous cell carcinoma (ESCC) cells and 1861 Kme1 sites in ESCC cells overexpressing SMYD2. Among these Kme1 sites is a subset of 35 found to be potently down-regulated by both shRNA-mediated knockdown of SMYD2 and LLY-507, a selective small molecule inhibitor of SMYD2. In addition, we report specific protein sequence motifs enriched in Kme1 sites that are directly regulated by endogenous SMYD2 activity, revealing that SMYD2 substrate specificity is more diverse than expected. We further show direct activity of SMYD2 toward BTF3-K2, PDAP1-K126 as well as numerous sites within the repetitive units of two unique and exceptionally large proteins, AHNAK and AHNAK2. Collectively, our findings provide quantitative insights into the cellular activity and substrate recognition of SMYD2 as well as the global landscape and regulation of protein mono-methylation.
Molecular & Cellular Poteomics2016. Olsen, JB et al.
Lilly USA, Lilly Res Labs, Indianapolis, IN 46285 USA.
ABSTRACT:The significance of non-histone lysine methylation in cell biology and human disease is an emerging area of research exploration. The development of small molecule inhibitors that selectively and potently target enzymes that catalyze the addition of methyl-groups to lysine residues, such as the protein lysine mono-methyltransferase SMYD2, is an active area of drug discovery. Critical to the accurate assessment of biological function is the ability to identify target enzyme substrates and to define enzyme substrate specificity within the context of the cell. Here, using stable isotopic labeling with amino acids in cell culture (SILAC) coupled with immunoaffinity enrichment of mono-methyl-lysine (Kme1) peptides and mass spectrometry, we report a comprehensive, large-scale proteomic study of lysine mono-methylation, comprising a total of 1032 Kme1 sites in esophageal squamous cell carcinoma (ESCC) cells and 1861 Kme1 sites in ESCC cells overexpressing SMYD2. Among these Kme1 sites is a subset of 35 found to be potently down-regulated by both shRNA-mediated knockdown of SMYD2 and LLY-507, a selective small molecule inhibitor of SMYD2. In addition, we report specific protein sequence motifs enriched in Kme1 sites that are directly regulated by endogenous SMYD2 activity, revealing that SMYD2 substrate specificity is more diverse than expected. We further show direct activity of SMYD2 toward BTF3-K2, PDAP1-K126 as well as numerous sites within the repetitive units of two unique and exceptionally large proteins, AHNAK and AHNAK2. Collectively, our findings provide quantitative insights into the cellular activity and substrate recognition of SMYD2 as well as the global landscape and regulation of protein mono-methylation.
Electrophoresis2016. Li, SS et al.
Nankai Univ, Coll Pharm, State Key Lab Med Chem Biol, Tianjin, Peoples R China.
ABSTRACT:O-linked beta-N-acetylglucosamine (O-GlcNAc) is emerging as an essential protein post-translational modification in a range of organisms. It is involved in various cellular processes such as nutrient sensing, protein degradation, gene expression, and is associated with many human diseases. Despite its importance, identifying O-GlcNAcylated proteins is a major challenge in proteomics. Here, using peracetylated N-azidoacetylglucosamine (Ac(4)GlcNAz) as a bioorthogonal chemical handle, we described a gel-based mass spectrometry method for the identification of proteins with O-GlcNAc modification in A549 cells. In addition, we made a labeling efficiency comparison between two modes of azide-alkyne bioorthogonal reactions in click chemistry: copper-catalyzed azide-alkyne cycloaddition (CuAAC) with Biotin-Diazo-Alkyne and stain-promoted azide-alkyne cycloaddition (SPAAC) with Biotin-DIBO-Alkyne. After conjugation with click chemistry in vitro and enrichment via streptavidin resin, proteins with O-GlcNAc modification were separated by SDS-PAGE and identified with mass spectrometry. Proteomics data analysis revealed that 229 putative O-GlcNAc modified proteins were identified with Biotin-Diazo-Alkyne conjugated sample and 188 proteins with Biotin-DIBO-Alkyne conjugated sample, among which 114 proteins were overlapping. Interestingly, 74 proteins identified from Biotin-Diazo-Alkyne conjugates and 46 verified proteins from Biotin-DIBO-Alkyne conjugates could be found in the O-GlcNAc modified proteins database dbOGAP (http://cbsb.lombardi.georgetown.edu/hulab/OGAP.html). These results suggested that CuAAC with Biotin-Diazo-Alkyne represented a more powerful method in proteomics with higher protein identification and better accuracy compared to SPAAC. The proteomics credibility was also confirmed by the molecular function and cell component gene ontology (GO). Together, the method we reported here combining metabolic labeling, click chemistry, affinity-based enrichment, SDS-PAGE separation, and mass spectrometry, would be adaptable for other post-translationally modified proteins in proteomics.
Journal of Proteome Research2016. Qiyao Li et al.
Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI, 53706;
ABSTRACT:A new global post-translational modification (PTM) discovery strategy, G-PTM-D, is described. A proteomics database containing UniProt-curated PTM information is supplemented with potential new modification types and sites discovered from a first-round search of mass spectrometry data with ultrawide precursor mass tolerance. A second-round search employing the supplemented database conducted with standard narrow mass tolerances yields deep coverage and a rich variety of peptide modifications with high confidence in complex unenriched samples. The G-PTM-D strategy represents a major advance to the previously reported G-PTM strategy and provides a powerful new capability to the proteomics research community.
Molecular & Cellular Proteomics2016. Wang, XS et al.
Univ Penn, Perelman Sch Med, Dept Biochem & Biophys, Epigenet Program, Room 9-124,3400 Civ Ctr Blvd,Bldg 421, Philadelphia, PA 19104 USA.
ABSTRACT:Over the past decades, protein O-GlcNAcylation has been found to play a fundamental role in cell cycle control, metabolism, transcriptional regulation, and cellular signaling. Nevertheless, quantitative approaches to determine in vivo GlcNAc dynamics at a large-scale are still not readily available. Here, we have developed an approach to isotopically label O-GlcNAc modifications on proteins by producing C-13-labeled UDP-GlcNAc from C-13(6)-glucose via the hexosamine biosynthetic pathway. This metabolic labeling was combined with quantitative mass spectrometry-based proteomics to determine protein O-GlcNAcylation turnover rates. First, an efficient enrichment method for O-GlcNAc peptides was developed with the use of phenylboronic acid solid-phase extraction and anhydrous DMSO. The near stoichiometry reaction between the diol of GlcNAc and boronic acid dramatically improved the enrichment efficiency. Additionally, our kinetic model for turnover rates integrates both metabolomic and proteomic data, which increase the accuracy of the turnover rate estimation. Other advantages of this metabolic labeling method include in vivo application, direct labeling of the O-GlcNAc sites and higher confidence for site identification. Concentrating only on nuclear localized GlcNAc modified proteins, we are able to identify 105 O-GlcNAc peptides on 42 proteins and determine turnover rates of 20 O-GlcNAc peptides from 14 proteins extracted from HeLa nuclei. In general, we found O-GlcNAcylation turnover rates are slower than those published for phosphorylation or acetylation. Nevertheless, the rates widely varied depending on both the protein and the residue modified. We believe this methodology can be broadly applied to reveal turnovers/dynamics of protein O-GlcNAcylation from different biological states and will provide more information on the significance of O-GlcNAcylation, enabling us to study the temporal dynamics of this critical modification for the first time.
Nucleic Acids Research2015. Trahan, C et al.
Inst Rech Clin Montreal, Dept Syst Biol, Montreal, PQ H2W 1R7, Canada.
ABSTRACT:Proteomic and RNomic approaches have identified many components of different ribonucleoprotein particles (RNPs), yet still little is known about the organization and protein proximities within these heterogeneous and highly dynamic complexes. Here we describe a targeted cross-linking approach, which combines cross-linking from a known anchor site with affinity purification and mass spectrometry (MS) to identify the changing vicinity interactomes along RNP maturation pathways. Our method confines the reaction radius of a heterobifunctional cross-linker to a specific interaction surface, increasing the probability to capture low abundance conformations and transient vicinal interactors too infrequent for identification by traditional cross-linking-MS approaches, and determine protein proximities within RNPs. Applying the method to two conserved RNA-associated complexes in Saccharomyces cerevisae, the mRNA export receptor Mex67:Mtr2 and the pre-ribosomal Nop7 subcomplex, we identified dynamic vicinal interactomes within those complexes and along their changing pathway milieu. Our results therefore show that this method provides a new tool to study the changing spatial organization of heterogeneous dynamic RNP complexes.
Methods2015. Rivera-Santiago, RF et al.
Wistar Inst Anat & Biol, 3601 Spruce St, Philadelphia, PA 19104 USA.
ABSTRACT:Structural mass spectrometry (MS) is a field with growing applicability for addressing complex biophysical questions regarding proteins and protein complexes. One of the major structural MS approaches involves the use of chemical cross-linking coupled with MS analysis (CX-MS) to identify proximal sites within macromolecules. Identified cross-linked sites can be used to probe novel protein-protein interactions or the derived distance constraints can be used to verify and refine molecular models. This review focuses on recent advances of "zero-length" cross-linking. Zero-length cross-linking reagents do not add any atoms to the cross-linked species due to the lack of a spacer arm. This provides a major advantage in the form of providing more precise distance constraints as the cross-linkable groups must be within salt bridge distances in order to react. However, identification of cross-linked peptides using these reagents presents unique challenges. We discuss recent efforts by our group to minimize these challenges by using multiple cycles of LC-MS/MS analysis and software specifically developed and optimized for identification of zero-length cross-linked peptides. Representative data utilizing our current protocol are presented and discussed. (C) 2015 Elsevier Inc. All rights reserved.
Molecular & Cellular Proteomics2015. Matthew M Makowski et al.
Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, Geert Grooteplein 28, 6525 GA Nijmegen, the Netherlands
ABSTRACT:In recent years, cross-linking mass spectrometry has proven to be a robust and effective methodofinterrogating macromolecularproteincomplex topologies at peptide resolution. Traditionally, cross-linking mass spectrometry workflows have utilized homogenouscomplexesobtained through time-limiting reconstitution, tandemaffinitypurification, and conventional chromatography workflows. Here, we present cross-linking immunoprecipitation-MS (xIP-MS), a simple, rapid, and efficient method for structurally probingchromatin-associatedproteincomplexesusingsmall volumesofmammalian whole cell lysates,singleaffinitypurification, and on-bead cross-linking followed by LC-MS/MSanalysis. We first benchmarkedxIP-MSusingthe structurally well-characterized phosphoribosyl pyrophosphate synthetase complex. We then appliedxIP-MSto thechromatin-associatedcohesin (SMC1A/3), XRCC5/6 (Ku70/86), and MCMcomplexes, and we provide novel structural and biological insights into their architectures and molecular function.Ofnote, we usexIP-MSto performtopologicalstudies under cell cycle perturbations, showing that thexIP-MSprotocol is sufficiently straightforward and efficient to allow comparative cross-linking experiments. This work, therefore, demonstrates thatxIP-MSis a robust, flexible, and widely applicable methodology for interrogatingchromatin-associatedproteincomplex architectures.
Science2015. Yan, CY et al.
Tsinghua Univ, Minist Educ, Key Lab Prot Sci,Sch Life Sci, Tsinghua Peking Joint Ctr Life Sci,Ctr Struct Bio, Beijing 100084, Peoples R China.
ABSTRACT:Splicing of precursor messenger RNA (pre-mRNA) in yeast is executed by the spliceosome, which consists of five small nuclear ribonucleoproteins (snRNPs), NTC (nineteen complex), NTC-related proteins (NTR), and a number of associated enzymes and cofactors. Here, we report the three-dimensional structure of a Schizosaccharomyces pombe spliceosome at 3.6-angstrom resolution, revealed by means of single-particle cryogenic electron microscopy. This spliceosome contains U2 and U5 snRNPs, NTC, NTR, U6 small nuclear RNA, and an RNA intron lariat. The atomic model includes 10,574 amino acids from 37 proteins and four RNA molecules, with a combined molecular mass of approximately 1.3 megadaltons. Spp42 (Prp8 in Saccharomyces cerevisiae), the key protein component of the U5 snRNP, forms a central scaffold and anchors the catalytic center. Both the morphology and the placement of protein components appear to have evolved to facilitate the dynamic process of pre-mRNA splicing. Our near-atomic-resolution structure of a central spliceosome provides a molecular framework for mechanistic understanding of pre-mRNA splicing.
Analytical Chemistry2015. He, L et al.
Scripps Res Inst, Dept Physiol Chem, 10550 North Torrey Pines Rd, La Jolla, CA 92037 USA.
ABSTRACT:Extraction of data from the proprietary RAW files generated by Thermo Fisher mass spectrometers is the primary step for subsequent data analysis. High resolution and high mass accuracy data obtained by state-of-the-art mass spectrometers (e.g., Orbitraps) can significantly improve both peptide/protein identification and quantification. We developed RawConverter, a stand-alone software tool, to improve data extraction on RAW files from high-resolution Thermo Fisher mass spectrometers. RawConverter extracts full scan and MS n data from RAW files like its predecessor RawXtract; most importantly, it associates the accurate precursor mass-tocharge (m/z) value with the tandem mass spectrum. RawConverter accepts RAW data generated by either data-dependent acquisition (DDA) or data-independent acquisition (DIA). It generates output into MS1/MS2/MS3, MGF, or mzXML file formats, which fulfills the format requirements for most data identification and quantification tools. Using the tandem mass spectra extracted by RawConverter with corrected m/z values, 32.8%, 27.1%, and 84.1%, peptide spectra matches (PSMs) produce 17.4% (13.0%), 14.4% (11.5%), and 45.7% (36.2%) more peptide (protein) identifications than ProteoWizard, pXtract, and RawXtract, respectively. RawConverter is implemented in C# and is freely accessible at http://fields.scripps.edu/rawconv.
Nature2014. Epshtein, V et al.
NYU, Sch Med, Dept Biochem & Mol Pharmacol, New York, NY 10016 USA.
ABSTRACT:UvrD helicase is required for nucleotide excision repair, although its role in this process is not well defined. Here we show that Escherichia coli UvrD binds RNA polymerase during transcription elongation and, using its helicase/translocase activity, forces RNA polymerase to slide backward along DNA. By inducing backtracking, UvrD exposes DNA lesions shielded by blocked RNA polymerase, allowing nucleotide excision repair enzymes to gain access to sites of damage. Our results establish UvrD as a bona fide transcription elongation factor that contributes to genomic integrity by resolving conflicts between transcription and DNA repair complexes. Furthermore, we show that the elongation factor NusA cooperates with UvrD in coupling transcription to DNA repair by promoting backtracking and recruiting nucleotide excision repair enzymes to exposed lesions. Because backtracking is a shared feature of all cellular RNA polymerases, we propose that this mechanism enables RNA polymerases to function as global DNA damage scanners in bacteria and eukaryotes.
Nature2014. Epshtein, V et al.
NYU, Sch Med, Dept Biochem & Mol Pharmacol, New York, NY 10016 USA.
ABSTRACT:UvrD helicase is required for nucleotide excision repair, although its role in this process is not well defined. Here we show that Escherichia coli UvrD binds RNA polymerase during transcription elongation and, using its helicase/translocase activity, forces RNA polymerase to slide backward along DNA. By inducing backtracking, UvrD exposes DNA lesions shielded by blocked RNA polymerase, allowing nucleotide excision repair enzymes to gain access to sites of damage. Our results establish UvrD as a bona fide transcription elongation factor that contributes to genomic integrity by resolving conflicts between transcription and DNA repair complexes. Furthermore, we show that the elongation factor NusA cooperates with UvrD in coupling transcription to DNA repair by promoting backtracking and recruiting nucleotide excision repair enzymes to exposed lesions. Because backtracking is a shared feature of all cellular RNA polymerases, we propose that this mechanism enables RNA polymerases to function as global DNA damage scanners in bacteria and eukaryotes.
Analytical Chemistry2014. Zhao, Q et al.
Chinese Acad Sci, Dalian Inst Chem Phys, Natl Chromatog R&A Ctr, Key Lab Separat Sci Analyt Chem, Dalian 116023, Liaoning, Peoples R China.
ABSTRACT:Due to their extremely hydrophobic nature, the analysis of integral membrane proteins (IMPs) is of great challenge. Although various additives have been applied to improve the solubility of IMPs, they still suffer from low solubilization efficiency, incompatibility with trypsin digestion, or interference with MS detection. Herein, the systematic study on the effect of ionic liquid structure on membrane protein solubilization and trypsin biocompatibility was performed, based on which 1-dodecyl-3-methylimidazolium chloride (C12Im-Cl) was selected for the sample preparation of IMPs. Compared with other commonly used additives, such as sodium dodecyl sulfate (SDS), Rapigest, and methanol, C12Im-Cl showed the best performance. In addition, with a strong cation exchange trap column, it could be easily removed after trypsin digestion, which not only was beneficial to avoid protein precipitation during digestion but also had no adverse effect on LC-MS-based separation and detection. Such a C12Im-Cl-assisted sample preparation method was further applied to the membrane proteome analysis of rat brain. Compared with the SDS-assisted method, 1.4 and 3.5 times improvement on the identified IMP and hydrophobic peptide number were achieved (251 vs 178, and 982 vs 279). All these results demonstrated that the C12Im-Cl-assisted sample preparation method is of great promise to promote the large-scale membrane proteome profiling.
Journal of proteome research2014. Cao, Liwei et al.
Chinese Acad Sci, Dalian Inst Chem Phys, Key Lab Separat Sci Analyt Chem, Dalian 116023, Peoples R China
ABSTRACT:N-Glycosylation site analysis of baker's yeast Saccharomyces cerevisiae is of fundamental significance to elucidate the molecular mechanism of human congenital disorders of glycosylation (CDG). Here we present a mass spectrometry (MS)-based workflow for the profiling of N-glycosylated sites in S. cerevisiae proteins. In this workflow, proteolytic glycopeptides were enriched by using a hydrophilic material named Click TE-Cys to improve the glycopeptide selectivity and coverage. To enhance the reliability of the identified results, the enriched glycopeptides were subjected to parallel deglycosylation by using two endoglycosidases (i.e., PNGase F and Endo H-f), respectively, prior to LC-MS/MS analysis. On the basis of the workflow, a total of 135 N-glycosylated sites including 6 known, 93 potential, and 36 novel sites were identified and mapped to 79 proteins. Among the novel-type sites, nine sites from eight proteins, which were simultaneously identified via PNGase F and Endo H-f deglycosylation, are believed to possess high confidence. The established workflow, together with the profile of N-glycosylated sites, will contribute to the improvement of S. cerevisiae model for revealing the pathogenesis of CDG.
Molecular & Cellular Proteomics2014. Liu, FY et al.
Chinese Acad Sci, Inst Hydrobiol, Key Lab Algal Biol, Wuhan 430072, Peoples R China.
ABSTRACT:The lysine acetylation of proteins is a reversible post-translational modification that plays a critical regulatory role in both eukaryotes and prokaryotes. Mycobacterium tuberculosis is a facultative intracellular pathogen and the causative agent of tuberculosis. Increasing evidence shows that lysine acetylation may play an important role in the pathogenesis of M. tuberculosis. However, only a few acetylated proteins of M. tuberculosis are known, presenting a major obstacle to understanding the functional roles of reversible lysine acetylation in this pathogen. We performed a global acetylome analysis of M. tuberculosis H37Ra by combining protein/peptide prefractionation, antibody enrichment, and LC-MS/MS. In total, we identified 226 acetylation sites in 137 proteins of M. tuberculosis H37Ra. The identified acetylated proteins were functionally categorized into an interaction map and shown to be involved in various biological processes. Consistent with previous reports, a large proportion of the acetylation sites were present on proteins involved in glycolysis/gluconeogenesis, the citrate cycle, and fatty acid metabolism. A NAD(+)-dependent deacetylase (MRA_1161) deletion mutant of M. tuberculosis H37Ra was constructed and its characterization showed a different colony morphology, reduced biofilm formation, and increased tolerance of heat stress. Interestingly, lysine acetylation was found, for the first time, to block the immunogenicity of a peptide derived from a known immunogen, HspX, suggesting that lysine acetylation plays a regulatory role in immunogenicity. Our data provide the first global survey of lysine acetylation in M. tuberculosis. The dataset should be an important resource for the functional analysis of lysine acetylation in M. tuberculosis and facilitate the clarification of the entire metabolic networks of this life-threatening pathogen.
Epigenetics2013. Cao, Xing-Jun et al.
Univ Penn, Dept Biochem & Biophys, Perelman Sch Med, Epigenet Program, 1009C Stellar Chance Labs, Philadelphia, PA 19104 USA
ABSTRACT:Lysine methylation mediated by methyltransferase enzymes is present on multiple proteins throughout the cell; however, methods to uncover and characterize global protein lysine methylation patterns do not readily exist. Here we developed pan-specific methyl lysine antibodies that we utilized in immunoprecipitation experiments coupled with mass spectrometry to yield one of the first large-scale surveys of protein lysine methylation in vivo. In total, 552 different lysine methylation sites were determined, making this one of the most comprehensive global studies published to date. The large majority of these sites have not been yet reported. These sites showed significantly enriched sequence motifs and resided in proteins that are involved in diverse biological processes, particularly in chromatin organization. Our data provide a comprehensive view of lysine methylation in human cells and a powerful resource to facilitate investigations into the function of lysine methylation on non-histone proteins.
Journal of Chromatography A2012. Jiang, H et al.
457 Zhongshan Rd, Dalian 116023, Peoples R China.
ABSTRACT:In this work, a novel kind of N-vinyl-2-pyrrolidinone (NVP) modified poly acrylic ester microspheres was prepared, followed by trypsin immobilization to prepare a hydrophilic immobilized enzyme reactor (IMER), to achieve highly efficient protein digestion with low peptide residue. The nonspecific adsorption of peptides on such an IMER was evaluated by the in sequence digestion of bovine serum albumin (BSA) and myoglobin. Without NVP modification, both proteins could be identified after digestion by a 5 cm-length IMER, but 18 peptides of BSA were found in the digests of myoglobin caused by the nonspecific adsorption of the matrix. With NVP modification, the hydrophilicity of IMER was greatly improved, resulting in not only the sequence coverage of myoglobin increased from 63% to 73%, but also no residual peptides from BSA observed in myoglobin digests. Although the sequence coverages of proteins obtained by the IMER were comparable to those obtained by in-solution digestion, the digestion time was shortened from 24 h to 1 min. By such an IMER, a protein mixture, containing BSA, myoglobin, and cytochrome c (100, 1 and 0.01 mu g/mL, respectively), was digested, and all proteins were unambiguously identified with improved sequence coverages than that achieved by in-solution digestion. Furthermore, the hydrophilic IMER was also off-line coupled to nano-RPLC-ESI-MS/MS for the analysis of proteins extracted from yeast. After 1.5 min digestion, 271 protein groups with at least 2 distinct peptides were identified, much more than those obtained by 24 h in-solution digestion (192 protein groups), indicating the great potential of such an IMER for proteome analysis. (C) 2012 Elsevier B.V. All rights reserved.
Analytical chemistry2013. Zhao, Qun et al.
Chinese Acad Sci, Dalian Inst Chem Phys, Key Lab Separat Sci Analyt Chem, Natl Chromatog R&A Ctr, Dalian 116023, Peoples R China
ABSTRACT:Combining good dissolving ability of formic acid (FA) for membrane proteins and excellent complementary retention behavior of proteins on strong cation exchange (SCX) and strong anion exchange (SAX) materials, a biphasic microreactor was established to pretreat membrane proteins at microgram and even nanogram levels. With membrane proteins solubilized by FA, all of the proteomics sample processing procedures, including protein preconcentration, pH adjustment, reduction, and alkylation, as well as tryptic digestion, were integrated into an "SCX-SAX" biphasic capillary column. To evaluate the performance of the developed microreactor, a mixture of bovine serum albumin, myoglobin, and cytochrome c was pretreated. Compared with the results obtained by the traditional in-solution process, the peptide recovery (93% vs 83%) and analysis throughput (3.5 vs 14 h) were obviously improved. The microreactor was further applied for the pretreatment of 14 mu g of membrane proteins extracted from rat cerebellums, and 416 integral membrane proteins (IMPs) (43% of total protein groups) and 103 transmembrane peptides were identified by two-dimensional nanoliquid chromatography-electrospray ionization tandem mass spectrometry (2D nano-LC-ESI-MS/MS) in triplicate analysis. With the starting sample preparation amount decreased to as low as 50 ng, 64 IMPs and 17 transmembrane peptides were identified confidently, while those obtained by the traditional in-solution method were 10 and 1, respectively. All these results demonstrated that such an "SCX-SAX" based biphasic microreactor could offer a promising tool for the pretreatment of trace membrane proteins with high efficiency and throughput.
Analytical and Bioanalytical Chemistry2013. Zhao, XY et al.
Beijing Inst Radiat Med, Beijing Proteome Res Ctr, State Key Lab Prote, Beijing 102206, Peoples R China.
ABSTRACT:Glycosylation is an important posttranslational modification of proteins and plays a crucial role in both cellular functions and secretory pathways. Sialic acids (SAs), a family of nine-carbon-containing acidic monosaccharides, often terminate the glycan structures of cell surface molecules and secreted glycoproteins and perform an important role in many biological processes. Hence, a more profound profiling of the sialylated glycoproteomics may improve our knowledge of this modification and its effects on protein functions. Here, we systematically investigated different strategies to enrich the SA proteins in human plasma using a newly developed technology that utilizes titanium dioxide for sialylated N-glycoproteomics profiling by mass spectrometry. Our results showed that using a combination of a filter-aided sample preparation method, TiO2 chromatography, multiple enzyme digestion, and two-dimensional reversed-phase peptide fractionation led to a more profound profiling of the SA proteome. In total, 982 glycosylation sites in 413 proteins were identified, among which 37.8 % were newly identified, to establish the largest database of sialic acid containing proteins from human plasma.
Analyst2012. Wu, Q et al.
Chinese Acad Sci, Dalian Inst Chem Phys, Key Lab Separat Sci Analyt Chem, Natl Chromatog Res & Anal Ctr, Dalian 116023, Peoples R China.
ABSTRACT:Although widely applied in the label-free quantification of proteomics, spectral count (SC)-based abundance measurements suffer from the narrow dynamic range of attainable ratios, leading to the serious underestimation of true protein abundance fold changes, especially when studying biological samples that exhibit very large fold changes in protein expression. MS/MS fragment ion intensity, as an alternative to SC, has recently gained acceptance as the abundance feature of protein in label-free proteomic studies. Herein, we implemented two formats of MS/MS fragment ion intensity, Spectral Index (SI) and Summed MS/MS TIC (SMT), to alleviate this particular deficiency arising from SC. Both were in forms of replacing SC in the Normalized Spectral Abundance Factor (NSAF) formula, resulting in two algorithms, abbreviated as NSI and NSMT, respectively. The necessity of the normalization process was validated using a publicly available dataset. Furthermore, when applied to another well characterized benchmark dataset, both NSI and NSMT showed improved overall accuracy over NSAF for the relative quantification of proteomes. Hereinto, NSI enabled the sensitive detection of differentially expressed proteins, while NSMT ensured accurate calculation for protein abundance fold change. Therefore, the selective use of both algorithms might facilitate the screening and quantification of potential biomarkers on the proteome scale.