1
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Lyutvinskiy Y, Nagornov KO, Kozhinov AN, Gasilova N, Menin L, Meng Z, Zhang X, Saei AA, Fu T, Chamot-Rooke J, Tsybin YO, Makarov A, Zubarev RA. Adding Color to Mass Spectra of Biopolymers: Charge Determination Analysis (CHARDA) Assigns Charge State to Every Ion Peak. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:902-911. [PMID: 38609335 PMCID: PMC11066971 DOI: 10.1021/jasms.3c00442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/06/2024] [Accepted: 04/04/2024] [Indexed: 04/14/2024]
Abstract
Traditionally, mass spectrometry (MS) output is the ion abundance plotted versus the ionic mass-to-charge ratio m/z. While employing only commercially available equipment, Charge Determination Analysis (CHARDA) adds a third dimension to MS, estimating for individual peaks their charge states z starting from z = 1 and color coding z in m/z spectra. CHARDA combines the analysis of ion signal decay rates in the time-domain data (transients) in Fourier transform (FT) MS with the interrogation of mass defects (fractional mass) of biopolymers. Being applied to individual isotopic peaks in a complex protein tandem (MS/MS) data set, CHARDA aids peptide mass spectra interpretation by facilitating charge-state deconvolution of large ionic species in crowded regions, estimating z even in the absence of an isotopic distribution (e.g., for monoisotopic mass spectra). CHARDA is fast, robust, and consistent with conventional FTMS and FTMS/MS data acquisition procedures. An effective charge-state resolution Rz ≥ 6 is obtained with the potential for further improvements.
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Affiliation(s)
- Yaroslav Lyutvinskiy
- Division
of Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden
| | | | | | - Natalia Gasilova
- Ecole
Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Laure Menin
- Ecole
Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Zhaowei Meng
- Division
of Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden
| | - Xuepei Zhang
- Division
of Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden
| | - Amir Ata Saei
- Division
of Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden
- Department
of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, United States
- Biozentrum, University of Basel, 4056 Basel, Switzerland
- Centre for
Translational Microbiome Research, Department of Microbiology, Tumor
and Cell Biology, Karolinska Institutet, Stockholm 17165, Sweden
| | | | | | | | | | - Roman A. Zubarev
- Division
of Chemistry I, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17 177 Stockholm, Sweden
- Department
of Pharmacological & Technological Chemistry, I.M., Sechenov First Moscow State Medical University, 119991 Moscow, Russia
- The National Medical Research
Center for Endocrinology, 115478 Moscow, Russia
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2
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Stauch KL, Totusek S, Trease AJ, Estrella LD, Emanuel K, Fangmeier A, Fox HS. Longitudinal in vivo metabolic labeling reveals tissue-specific mitochondrial proteome turnover rates and proteins selectively altered by parkin deficiency. Sci Rep 2023; 13:11414. [PMID: 37452120 PMCID: PMC10349111 DOI: 10.1038/s41598-023-38484-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 07/09/2023] [Indexed: 07/18/2023] Open
Abstract
Our study utilizes a longitudinal isotopic metabolic labeling approach in vivo in combination with organelle fraction proteomics to address the role of parkin in mitochondrial protein turnover in mice. The use of metabolic labeling provides a method to quantitatively determine the global changes in protein half-lives whilst simultaneously assessing protein expression. Studying two diverse mitochondrial populations, we demonstrated the median half-life of brain striatal synaptic mitochondrial proteins is significantly greater than that of hepatic mitochondrial proteins (25.7 vs. 3.5 days). Furthermore, loss of parkin resulted in an overall, albeit modest, increase in both mitochondrial protein abundance and half-life. Pathway and functional analysis of our proteomics data identified both known and novel pathways affected by loss of parkin that are consistent with its role in both mitochondrial quality control and neurodegeneration. Our study therefore adds to a growing body of evidence suggesting dependence on parkin is low for basal mitophagy in vivo and provides a foundation for the investigation of novel parkin targets.
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Affiliation(s)
- K L Stauch
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - S Totusek
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - A J Trease
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - L D Estrella
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - K Emanuel
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - A Fangmeier
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - H S Fox
- Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, USA.
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3
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Zhou C, Dai S, Lin Y, Lian S, Fan X, Li N, Yu W. Exhaustive Cross-Linking Search with Protein Feedback. J Proteome Res 2023; 22:101-113. [PMID: 36480279 DOI: 10.1021/acs.jproteome.2c00500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Improving the sensitivity of protein-protein interaction detection and protein structure probing is a principal challenge in cross-linking mass spectrometry (XL-MS) data analysis. In this paper, we propose an exhaustive cross-linking search method with protein feedback (ECL-PF) for cleavable XL-MS data analysis. ECL-PF adopts an optimized α/β mass detection scheme and establishes protein-peptide association during the identification of cross-linked peptides. Existing major scoring functions can all benefit from the ECL-PF workflow to a great extent. In comparisons using synthetic data sets and hybrid simulated data sets, ECL-PF achieved 3-fold higher sensitivity over standard techniques. In experiments using real data sets, it also identified 65.6% more cross-link spectrum matches and 48.7% more unique cross-links.
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Affiliation(s)
- Chen Zhou
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
| | - Shuaijian Dai
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong 999077, China
| | - Yuanqiao Lin
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
| | - Sheng Lian
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China
| | - Xiaodan Fan
- Department of Statistics, The Chinese University of Hong Kong, Hong Kong 999077, China
| | - Ning Li
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong 999077, China.,HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Futian, Shenzhen, 518000, China
| | - Weichuan Yu
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong 999077, China.,HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute, Futian, Shenzhen, 518000, China
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4
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Teo GC, Polasky DA, Yu F, Nesvizhskii AI. Fast Deisotoping Algorithm and Its Implementation in the MSFragger Search Engine. J Proteome Res 2020; 20:498-505. [PMID: 33332123 DOI: 10.1021/acs.jproteome.0c00544] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Deisotoping, or the process of removing peaks in a mass spectrum resulting from the incorporation of naturally occurring heavy isotopes, has long been used to reduce complexity and improve the effectiveness of spectral annotation methods in proteomics. We have previously described MSFragger, an ultrafast search engine for proteomics, that did not utilize deisotoping in processing input spectra. Here, we present a new, high-speed parallelized deisotoping algorithm, based on elements of several existing methods, that we have incorporated into the MSFragger search engine. Applying deisotoping with MSFragger reveals substantial improvements to database search speed and performance, particularly for complex methods like open or nonspecific searches. Finally, we evaluate our deisotoping method on data from several instrument types and vendors, revealing a wide range in performance and offering an updated perspective on deisotoping in the modern proteomics environment.
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Affiliation(s)
- Guo Ci Teo
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Daniel A Polasky
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Fengchao Yu
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alexey I Nesvizhskii
- Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, United States.,Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
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5
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Rad R, Li J, Mintseris J, O'Connell J, Gygi SP, Schweppe DK. Improved Monoisotopic Mass Estimation for Deeper Proteome Coverage. J Proteome Res 2020; 20:591-598. [PMID: 33190505 DOI: 10.1021/acs.jproteome.0c00563] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Accurate assignment of monoisotopic peaks is essential for the identification of peptides in bottom-up proteomics. Misassignment or inaccurate attribution of peptidic ions leads to lower sensitivity and fewer total peptide identifications. In the present work, we present a performant, open-source, cross-platform algorithm, Monocle, for the rapid reassignment of instrument-assigned precursor peaks to monoisotopic peptide assignments. We demonstrate that the present algorithm can be integrated into many common proteomic pipelines and provides rapid conversion from multiple data source types. Finally, we show that our monoisotopic peak assignment results in up to a twofold increase in total peptide identifications compared to analyses lacking monoisotopic correction and a 44% improvement over previous monoisotopic peak correction algorithms.
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Affiliation(s)
- Ramin Rad
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Jiaming Li
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Julian Mintseris
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Jeremy O'Connell
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, United States
| | - Devin K Schweppe
- Department of Genome Sciences, University of Washington, 3720 15th Ave NE, Seattle, Washington 98105, United States
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6
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Makepeace KAT, Mohammed Y, Rudashevskaya EL, Petrotchenko EV, Vögtle FN, Meisinger C, Sickmann A, Borchers CH. Improving Identification of In-organello Protein-Protein Interactions Using an Affinity-enrichable, Isotopically Coded, and Mass Spectrometry-cleavable Chemical Crosslinker. Mol Cell Proteomics 2020; 19:624-639. [PMID: 32051233 PMCID: PMC7124466 DOI: 10.1074/mcp.ra119.001839] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 01/17/2020] [Indexed: 12/24/2022] Open
Abstract
An experimental and computational approach for identification of protein-protein interactions by ex vivo chemical crosslinking and mass spectrometry (CLMS) has been developed that takes advantage of the specific characteristics of cyanurbiotindipropionylsuccinimide (CBDPS), an affinity-tagged isotopically coded mass spectrometry (MS)-cleavable crosslinking reagent. Utilizing this reagent in combination with a crosslinker-specific data-dependent acquisition strategy based on MS2 scans, and a software pipeline designed for integrating crosslinker-specific mass spectral information led to demonstrated improvements in the application of the CLMS technique, in terms of the detection, acquisition, and identification of crosslinker-modified peptides. This approach was evaluated on intact yeast mitochondria, and the results showed that hundreds of unique protein-protein interactions could be identified on an organelle proteome-wide scale. Both known and previously unknown protein-protein interactions were identified. These interactions were assessed based on their known sub-compartmental localizations. Additionally, the identified crosslinking distance constraints are in good agreement with existing structural models of protein complexes involved in the mitochondrial electron transport chain.
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Affiliation(s)
- Karl A T Makepeace
- Department of Biochemistry and Microbiology, University of Victoria, 3800 Finnerty Rd., Victoria, BC V8P 5C2, Canada; University of Victoria - Genome British Columbia Proteomics Centre, #3101-4464 Markham Street, Vancouver Island Technology Park, Victoria, BC V8Z7X8, Canada
| | - Yassene Mohammed
- University of Victoria - Genome British Columbia Proteomics Centre, #3101-4464 Markham Street, Vancouver Island Technology Park, Victoria, BC V8Z7X8, Canada; Center for Proteomics and Metabolomics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands
| | | | - Evgeniy V Petrotchenko
- University of Victoria - Genome British Columbia Proteomics Centre, #3101-4464 Markham Street, Vancouver Island Technology Park, Victoria, BC V8Z7X8, Canada; Segal Cancer Proteomics Centre, Lady Davis Institute, Jewish General Hospital, McGill University, Montreal, Quebec, H3T 1E2, Canada
| | - F-Nora Vögtle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Germany
| | - Chris Meisinger
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany; Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Germany
| | - Albert Sickmann
- Leibniz Institut für Analytische Wissenschaften - ISAS - e.V., Dortmund, Germany.
| | - Christoph H Borchers
- Department of Biochemistry and Microbiology, University of Victoria, 3800 Finnerty Rd., Victoria, BC V8P 5C2, Canada; University of Victoria - Genome British Columbia Proteomics Centre, #3101-4464 Markham Street, Vancouver Island Technology Park, Victoria, BC V8Z7X8, Canada; Segal Cancer Proteomics Centre, Lady Davis Institute, Jewish General Hospital, McGill University, Montreal, Quebec, H3T 1E2, Canada; Gerald Bronfman Department of Oncology, Jewish General Hospital, Montreal, Quebec, H3T 1E2, Canada; Department of Data Intensive Science and Engineering, Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Nobel St., Moscow 143026, Russia.
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7
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Sulfur- 34S and 36S Stable Isotope Labeling of Amino Acids for Quantification (SULAQ34/36) of Proteome Analyses. Methods Mol Biol 2018. [PMID: 30259486 DOI: 10.1007/978-1-4939-8695-8_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Quantitative proteome profiling of microorganisms by isotopic labeling of amino acids is still a challenge, because only microorganisms with auxotrophic character are able to embed amino acids into their biomass in a quantitatively correct manner. Here, we describe an isotopic labeling technique (sulfur stable isotope labeling of amino acids for quantification, SULAQ) for the sulfur-containing amino acids cysteine and methionine in a broad range of organisms. The metabolic labeling approach is suitable for gel-based and gel-free protein analysis.
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8
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Sychev ZE, Hu A, DiMaio TA, Gitter A, Camp ND, Noble WS, Wolf-Yadlin A, Lagunoff M. Integrated systems biology analysis of KSHV latent infection reveals viral induction and reliance on peroxisome mediated lipid metabolism. PLoS Pathog 2017; 13:e1006256. [PMID: 28257516 PMCID: PMC5352148 DOI: 10.1371/journal.ppat.1006256] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 03/15/2017] [Accepted: 02/22/2017] [Indexed: 12/22/2022] Open
Abstract
Kaposi’s Sarcoma associated Herpesvirus (KSHV), an oncogenic, human gamma-herpesvirus, is the etiological agent of Kaposi’s Sarcoma the most common tumor of AIDS patients world-wide. KSHV is predominantly latent in the main KS tumor cell, the spindle cell, a cell of endothelial origin. KSHV modulates numerous host cell-signaling pathways to activate endothelial cells including major metabolic pathways involved in lipid metabolism. To identify the underlying cellular mechanisms of KSHV alteration of host signaling and endothelial cell activation, we identified changes in the host proteome, phosphoproteome and transcriptome landscape following KSHV infection of endothelial cells. A Steiner forest algorithm was used to integrate the global data sets and, together with transcriptome based predicted transcription factor activity, cellular networks altered by latent KSHV were predicted. Several interesting pathways were identified, including peroxisome biogenesis. To validate the predictions, we showed that KSHV latent infection increases the number of peroxisomes per cell. Additionally, proteins involved in peroxisomal lipid metabolism of very long chain fatty acids, including ABCD3 and ACOX1, are required for the survival of latently infected cells. In summary, novel cellular pathways altered during herpesvirus latency that could not be predicted by a single systems biology platform, were identified by integrated proteomics and transcriptomics data analysis and when correlated with our metabolomics data revealed that peroxisome lipid metabolism is essential for KSHV latent infection of endothelial cells. Kaposi’s Sarcoma herpesvirus (KSHV) is the etiologic agent of Kaposi’s Sarcoma, the most common tumor of AIDS patients. KSHV modulates host cell signaling and metabolism to maintain a life-long latent infection. To unravel the underlying cellular mechanisms modulated by KSHV, we used multiple global systems biology platforms to identify and integrate changes in both cellular protein expression and transcription following KSHV infection of endothelial cells, the relevant cell type for KS tumors. The analysis identified several interesting pathways including peroxisome biogenesis. Peroxisomes are small cytoplasmic organelles involved in redox reactions and lipid metabolism. KSHV latent infection increases the number of peroxisomes per cell and proteins involved in peroxisomal lipid metabolism are required for the survival of latently infected cells. In summary, through integration of multiple global systems biology analyses we were able to identify novel pathways that could not be predicted by one platform alone and found that lipid metabolism in a small cytoplasmic organelle is necessary for the survival of latent infection with a herpesvirus.
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Affiliation(s)
- Zoi E. Sychev
- Molecular and Cellular Biology Program, University of Washington, Seattle, Washington, United States of America
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Alex Hu
- Department of Genome Science, University of Washington, Seattle, Washington, United States of America
| | - Terri A. DiMaio
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Anthony Gitter
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison and Morgridge Institute for Research, Madison, Wisconsin, USA
| | - Nathan D. Camp
- Department of Genome Science, University of Washington, Seattle, Washington, United States of America
| | - William S. Noble
- Department of Genome Science, University of Washington, Seattle, Washington, United States of America
| | - Alejandro Wolf-Yadlin
- Department of Genome Science, University of Washington, Seattle, Washington, United States of America
- * E-mail: (ML); (AWY)
| | - Michael Lagunoff
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- * E-mail: (ML); (AWY)
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9
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N-linked glycosite profiling and use of Skyline as a platform for characterization and relative quantification of glycans in differentiating xylem of Populus trichocarpa. Anal Bioanal Chem 2016; 409:487-497. [PMID: 27491298 DOI: 10.1007/s00216-016-9776-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 06/28/2016] [Accepted: 07/06/2016] [Indexed: 01/02/2023]
Abstract
Our greater understanding of the importance of N-linked glycosylation in biological systems has spawned the field of glycomics and development of analytical tools to address the many challenges regarding our ability to characterize and quantify this complex and important modification as it relates to biological function. One of the unmet needs of the field remains a systematic method for characterization of glycans in new biological systems. This study presents a novel workflow for identification of glycans using Individuality Normalization when Labeling with Isotopic Glycan Hydrazide Tags (INLIGHT™) strategy developed in our lab. This consists of monoisotopic mass extraction followed by peak pair identification of tagged glycans from a theoretical library using an in-house program. Identification and relative quantification could then be performed using the freely available bioinformatics tool Skyline. These studies were performed in the biological context of studying the N-linked glycome of differentiating xylem of the poplar tree, a widely studied model woody plant, particularly with respect to understanding lignin biosynthesis during wood formation. Through our workflow, we were able to identify 502 glycosylated proteins including 12 monolignol enzymes and 1 peroxidase (PO) through deamidation glycosite analysis. Finally, our novel semi-automated workflow allowed for rapid identification of 27 glycans by intact mass and by NAT/SIL peak pairing from a library containing 1573 potential glycans, eliminating the need for extensive manual analysis. Implementing Skyline for relative glycan quantification allowed for improved accuracy and precision of quantitative measurements over current processing tools which we attribute to superior algorithms correction for baseline variation and MS1 peak filtering. Graphical abstract Workflow for FANGS-INLIGHT glycosite profiling of plant xylem and monolignol proteins followed by INLIGHT tagging with semi-automated identification of glycans by light-heavy peak pairs. Finally, manual validation and relative quantification was performed in Skyline.
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10
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Shteynberg D, Mendoza L, Hoopmann MR, Sun Z, Schmidt F, Deutsch EW, Moritz RL. reSpect: software for identification of high and low abundance ion species in chimeric tandem mass spectra. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:1837-1847. [PMID: 26419769 PMCID: PMC4750398 DOI: 10.1007/s13361-015-1252-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/22/2015] [Accepted: 08/11/2015] [Indexed: 06/05/2023]
Abstract
Most shotgun proteomics data analysis workflows are based on the assumption that each fragment ion spectrum is explained by a single species of peptide ion isolated by the mass spectrometer; however, in reality mass spectrometers often isolate more than one peptide ion within the window of isolation that contribute to additional peptide fragment peaks in many spectra. We present a new tool called reSpect, implemented in the Trans-Proteomic Pipeline (TPP), which enables an iterative workflow whereby fragment ion peaks explained by a peptide ion identified in one round of sequence searching or spectral library search are attenuated based on the confidence of the identification, and then the altered spectrum is subjected to further rounds of searching. The reSpect tool is not implemented as a search engine, but rather as a post-search engine processing step where only fragment ion intensities are altered. This enables the application of any search engine combination in the iterations that follow. Thus, reSpect is compatible with all other protein sequence database search engines as well as peptide spectral library search engines that are supported by the TPP. We show that while some datasets are highly amenable to chimeric spectrum identification and lead to additional peptide identification boosts of over 30% with as many as four different peptide ions identified per spectrum, datasets with narrow precursor ion selection only benefit from such processing at the level of a few percent. We demonstrate a technique that facilitates the determination of the degree to which a dataset would benefit from chimeric spectrum analysis. The reSpect tool is free and open source, provided within the TPP and available at the TPP website. Graphical Abstract ᅟ.
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Affiliation(s)
| | | | | | - Zhi Sun
- Institute for Systems Biology, Seattle, WA, USA
| | - Frank Schmidt
- ZIK-FunGene Junior Research Group Applied Proteomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
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11
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Herbst FA, Taubert M, Jehmlich N, Behr T, Schmidt F, von Bergen M, Seifert J. Sulfur-34S stable isotope labeling of amino acids for quantification (SULAQ34) of proteomic changes in Pseudomonas fluorescens during naphthalene degradation. Mol Cell Proteomics 2013; 12:2060-9. [PMID: 23603340 DOI: 10.1074/mcp.m112.025627] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The relative quantification of proteins is one of the major techniques used to elucidate physiological reactions. Because it allows one to avoid artifacts due to chemical labeling, the metabolic introduction of heavy isotopes into proteins and peptides is the preferred method for relative quantification. For eukaryotic cells, stable isotope labeling by amino acids in cell culture (SILAC) has become the gold standard and can be readily applied in a vast number of scenarios. In the microbial realm, with its highly versatile metabolic capabilities, SILAC is often not feasible, and the use of other (13)C or (15)N labeled substrates might not be practical. Here, the incorporation of heavy sulfur isotopes is shown to be a useful alternative. We introduce (34)S stable isotope labeling of amino acids for quantification and the corresponding tools required for spectra extraction and disintegration of the isotopic overlaps caused by the small mass shift. As proof of principle, we investigated the proteomic changes related to naphthalene degradation in P. fluorescens ATCC 17483 and uncovered a specific oxidative-stress-like response.
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Affiliation(s)
- Florian-Alexander Herbst
- Helmholtz Centre for Environmental Research, Department of Proteomics, Permoserstrasse 15, 04318 Leipzig, Germany
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