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Phetsanthad A, Vu NQ, Yu Q, Buchberger AR, Chen Z, Keller C, Li L. Recent advances in mass spectrometry analysis of neuropeptides. MASS SPECTROMETRY REVIEWS 2023; 42:706-750. [PMID: 34558119 PMCID: PMC9067165 DOI: 10.1002/mas.21734] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 08/22/2021] [Accepted: 08/28/2021] [Indexed: 05/08/2023]
Abstract
Due to their involvement in numerous biochemical pathways, neuropeptides have been the focus of many recent research studies. Unfortunately, classic analytical methods, such as western blots and enzyme-linked immunosorbent assays, are extremely limited in terms of global investigations, leading researchers to search for more advanced techniques capable of probing the entire neuropeptidome of an organism. With recent technological advances, mass spectrometry (MS) has provided methodology to gain global knowledge of a neuropeptidome on a spatial, temporal, and quantitative level. This review will cover key considerations for the analysis of neuropeptides by MS, including sample preparation strategies, instrumental advances for identification, structural characterization, and imaging; insightful functional studies; and newly developed absolute and relative quantitation strategies. While many discoveries have been made with MS, the methodology is still in its infancy. Many of the current challenges and areas that need development will also be highlighted in this review.
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Affiliation(s)
- Ashley Phetsanthad
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Nhu Q. Vu
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Qing Yu
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
| | - Amanda R. Buchberger
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Zhengwei Chen
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Caitlin Keller
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
| | - Lingjun Li
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
- School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
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2
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Wang R, Wang Z, Lu H. Separation methods for system-wide profiling of protein terminome. Proteomics 2023; 23:e2100374. [PMID: 35997653 DOI: 10.1002/pmic.202100374] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 08/07/2022] [Accepted: 08/09/2022] [Indexed: 11/10/2022]
Abstract
Protein N- and C-termini have specific biochemical properties and functions. They play vital roles in various biological processes, such as protein stability and localization. In addition, post-translational modifications and proteolytic processing generate different proteoforms at protein termini. In recent years, terminomics has attracted significant attention, and numerous strategies have been developed to achieve high-throughput and global terminomics analysis. This review summarizes the recent protein N-termini and C-termini enrichment methods and their application in different samples. We also look ahead further application of terminomics in profiling protease substrates and discovery of disease biomarkers and therapeutic targets.
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Affiliation(s)
- Rui Wang
- Shanghai Cancer Center and Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China
| | - Zhongjie Wang
- Shanghai Cancer Center and Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China
| | - Haojie Lu
- Shanghai Cancer Center and Institutes of Biomedical Sciences, Fudan University, Shanghai, People's Republic of China.,Department of Chemistry and Key Laboratory of Glycoconjugates Research Ministry of Public Health, Fudan University, Shanghai, People's Republic of China
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3
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Zhang L, Floyd BM, Chilamari M, Mapes J, Swaminathan J, Bloom S, Marcotte EM, Anslyn EV. Photoredox-Catalyzed Decarboxylative C-Terminal Differentiation for Bulk- and Single-Molecule Proteomics. ACS Chem Biol 2021; 16:2595-2603. [PMID: 34734691 DOI: 10.1021/acschembio.1c00631] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Methods for the selective labeling of biogenic functional groups on peptides are being developed and used in the workflow of both current and emerging proteomics technologies, such as single-molecule fluorosequencing. To achieve successful labeling with any one method requires that the peptide fragments contain the functional group for which labeling chemistry is designed. In practice, only two functional groups are present in every peptide fragment regardless of the protein cleavage site, namely, an N-terminal amine and a C-terminal carboxylic acid. Developing a global-labeling technology, therefore, requires one to specifically target the N- and/or C-terminus of peptides. In this work, we showcase the first successful application of photocatalyzed C-terminal decarboxylative alkylation for peptide mass spectrometry and single-molecule protein sequencing that can be broadly applied to any proteome. We demonstrate that peptides in complex mixtures generated from enzymatic digests from bovine serum albumin, as well as protein mixtures from yeast and human cell extracts, can be site-specifically labeled at their C-terminal residue with a Michael acceptor. Using two distinct analytical approaches, we characterize C-terminal labeling efficiencies of greater than 50% across complete proteomes and document the proclivity of various C-terminal amino-acid residues for decarboxylative labeling, showing histidine and tryptophan to be the most disfavored. Finally, we combine C-terminal decarboxylative labeling with an orthogonal carboxylic acid-labeling technology in tandem to establish a new platform for fluorosequencing.
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Affiliation(s)
- Le Zhang
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Brendan M. Floyd
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Maheshwerreddy Chilamari
- School of Pharmacy - Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045-7572, United States
| | - James Mapes
- Erisyon, Inc., Austin, Texas 78701, United States
| | - Jagannath Swaminathan
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Steven Bloom
- School of Pharmacy - Medicinal Chemistry, University of Kansas, Lawrence, Kansas 66045-7572, United States
| | - Edward M. Marcotte
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Eric V. Anslyn
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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4
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Application of a fluorous derivatization method for characterization of glutathione-trapped reactive metabolites with liquid chromatography-tandem mass spectrometry analysis. J Chromatogr A 2020; 1622:461160. [PMID: 32450990 DOI: 10.1016/j.chroma.2020.461160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 04/13/2020] [Accepted: 04/21/2020] [Indexed: 01/05/2023]
Abstract
The glutathione (GSH) trapping assay is commonly utilized for the screening and characterization of reactive metabolites produced by drug metabolism. This study describes a fluorous derivatization method for a more sensitive and selective analysis of reactive metabolites trapped by GSH using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this study, the GSH-trapped reactive metabolites, which were obtained after incubation of the test compounds with human liver microsome (HLM) in the presence of GSH and NADPH, were derivatized using the perfluoroalkylamine reagent through oxazolone chemistry. Since this reaction enabled the selective modification of the α-carboxyl group in GSH, the structural compositions of the metabolites were not affected by the derivatization. Furthermore, the selective analysis of the resulting derivatives could be performed using perfluoroalkyl-modified stationary phase LC separation via the interaction between the perfluoroalkyl-containing compounds, such as fluorous affinity, followed by detection with the precursor ion and/or enhanced product ion scan modes in MS/MS. Finally, we demonstrated the applicability of this method by analyzing perfluoroalkyl derivatives of some drug metabolites trapped by GSH in HLM incubation.
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Zhang J, Jia S, Lu W, Li W, Jiang R, Liu Y, Yang X, Zou S, Zou X, Zhong H. Real-time laser induced chemical derivatizations of peptide N-Terminus for in-situ mass spectrometric sequencing at sub-picomole and nanosecond scale. Anal Chim Acta 2019; 1100:1-11. [PMID: 31987129 DOI: 10.1016/j.aca.2019.12.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/10/2019] [Accepted: 12/12/2019] [Indexed: 11/30/2022]
Abstract
Distinguishing b- and y-ions is essential to compute amino acid sequences from either N- or C-terminus in mass spectrometry. We described herein a solvent free and real time on-plate derivatization approach that can tag N-terminus of peptides at microliter level with p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde for matrix assisted laser desorption ionization mass spectrometry (MALDI MS). Less than 1 μL of sample solutions can be directly mixed with equal volumes of p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde and α-cyano-4-hydroxycinnamic acid (CHCA), a matrix compound to co-crystalize with analytes for efficient absorption of laser energy and peptide ionization. When the mixture spotted on the sample plate is irradiated with the 3rd harmonic (355 nm) of Nd3+:YAG laser pulses (3 ns width), N-terminal amine groups of peptides instantly react with carbonyl groups of chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde. Resultant peptides carrying with on-plate formed azomethine group (-CN-) are simultaneously protonated and isolated as precursor ions for subsequent collision-activated dissociation. The mass shift with unique Cl isotopic signature unambiguously distinguishes b ions from y ions and other ions. This method does not need extensive sample preparation and is useful for those samples with limited quantities down to sub-picomole level in sub-microliter volumes. The efficiency was demonstrated with synthetic peptides and tryptic peptides of model proteins. It was found that 2-hydroxy-5-methylisophthalaldehyde provides improved yield for peptides containing lysine residues. Unknown proteins of human saliva and bovine milk as well as phosphopeptides have been identified.
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Affiliation(s)
- Juan Zhang
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Shanshan Jia
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Wenting Lu
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Weidan Li
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Ruowei Jiang
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Yanping Liu
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Xiaojie Yang
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Si Zou
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Xuekun Zou
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China
| | - Hongying Zhong
- Laboratory of Mass Spectrometry, College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, PR China; Key Laboratory of Pesticides and Chemical Biology, Ministry of Education, PR China.
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6
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Hage C, Falvo F, Schäfer M, Sinz A. Novel Concepts of MS-Cleavable Cross-linkers for Improved Peptide Structure Analysis. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2022-2038. [PMID: 28653243 DOI: 10.1007/s13361-017-1712-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 05/03/2017] [Accepted: 05/07/2017] [Indexed: 06/07/2023]
Abstract
The chemical cross-linking/mass spectrometry (MS) approach is gaining increasing importance as an alternative method for studying protein conformation and for deciphering protein interaction networks. This study is part of our ongoing efforts to develop innovative cross-linking principles for a facile and efficient assignment of cross-linked products. We evaluate two homobifunctional, amine-reactive, and MS-cleavable cross-linkers regarding their potential for automated analysis of cross-linked products. We introduce the bromine phenylurea (BrPU) linker that possesses a unique structure yielding a distinctive fragmentation pattern on collisional activation. Moreover, BrPU delivers the characteristic bromine isotope pattern and mass defect for all cross-linker-decorated fragments. We compare the fragmentation behavior of the BrPU linker with that of our previously described MS-cleavable TEMPO-Bz linker (which consists of a 2,2,6,6-tetramethylpiperidine-1-oxy moiety connected to a benzyl group) that was developed to perform free-radical-initiated peptide sequencing. Comparative collisional activation experiments (collision-induced dissociation and higher-energy collision-induced dissociation) with both cross-linkers were conducted in negative electrospray ionization mode with an Orbitrap Fusion mass spectrometer using five model peptides. As hypothesized in a previous study, the presence of a cross-linked N-terminal aspartic acid residue seems to be the prerequisite for the loss of an intact peptide from the cross-linked products. As the BrPU linker combines a characteristic mass shift with an isotope signature, it presents a more favorable combination for automated assignment of cross-linked products compared with the TEMPO-Bz linker. ᅟ.
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Affiliation(s)
- Christoph Hage
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120, Halle (Saale), Germany
| | - Francesco Falvo
- Department of Chemistry, University of Cologne, Greinstr. 4, 50939, Cologne, Germany
- Eurofins Umwelt West GmbH, Vorgebirgsstr. 20, 50389, Wesseling, Germany
| | - Mathias Schäfer
- Department of Chemistry, University of Cologne, Greinstr. 4, 50939, Cologne, Germany
| | - Andrea Sinz
- Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120, Halle (Saale), Germany.
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7
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Nam J, Kwon H, Jang I, Jeon A, Moon J, Lee SY, Kang D, Han SY, Moon B, Oh HB. Bromine isotopic signature facilitates de novo sequencing of peptides in free-radical-initiated peptide sequencing (FRIPS) mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2015; 50:378-387. [PMID: 25800020 DOI: 10.1002/jms.3539] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 08/04/2014] [Accepted: 11/02/2014] [Indexed: 06/04/2023]
Abstract
We recently showed that free-radical-initiated peptide sequencing mass spectrometry (FRIPS MS) assisted by the remarkable thermochemical stability of (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) is another attractive radical-driven peptide fragmentation MS tool. Facile homolytic cleavage of the bond between the benzylic carbon and the oxygen of the TEMPO moiety in o-TEMPO-Bz-C(O)-peptide and the high reactivity of the benzylic radical species generated in •Bz-C(O)-peptide are key elements leading to extensive radical-driven peptide backbone fragmentation. In the present study, we demonstrate that the incorporation of bromine into the benzene ring, i.e. o-TEMPO-Bz(Br)-C(O)-peptide, allows unambiguous distinction of the N-terminal peptide fragments from the C-terminal fragments through the unique bromine doublet isotopic signature. Furthermore, bromine substitution does not alter the overall radical-driven peptide backbone dissociation pathways of o-TEMPO-Bz-C(O)-peptide. From a practical perspective, the presence of the bromine isotopic signature in the N-terminal peptide fragments in TEMPO-assisted FRIPS MS represents a useful and cost-effective opportunity for de novo peptide sequencing.
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Affiliation(s)
- Jungjoo Nam
- Department of Chemistry, Sogang University, Seoul, 121-742, Korea
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8
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Tanco S, Gevaert K, Van Damme P. C-terminomics: Targeted analysis of natural and posttranslationally modified protein and peptide C-termini. Proteomics 2014; 15:903-14. [PMID: 25316308 DOI: 10.1002/pmic.201400301] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 09/03/2014] [Accepted: 10/09/2014] [Indexed: 01/03/2023]
Abstract
The C-terminus (where C is carboxyl) of a protein can serve as a recognition signature for a variety of biological processes, including protein trafficking and protein complex formation. Hence, the identity of the in vivo protein C-termini provides valuable information about biological processes. Analysis of protein C-termini is also crucial for the study of C-terminal PTMs, particularly for monitoring proteolytic processing by endopeptidases and carboxypeptidases. Although technical difficulties have limited the study of C-termini, a range of technologies have been proposed in the last couple of years. Here, we review the current proteomics technologies for C-terminal analysis, with a focus on the biological information that can be derived from C-terminomics studies.
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Affiliation(s)
- Sebastian Tanco
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Ghent University, Ghent, Belgium
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9
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Moerman P, Sergeant K, Debyser G, Timperman I, Devreese B, Samyn B. Automation of C-terminal sequence analysis of 2D-PAGE separated proteins. EUPA OPEN PROTEOMICS 2014. [DOI: 10.1016/j.euprot.2014.03.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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11
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Liu M, Zhang L, Zhang L, Yao J, Yang P, Lu H. Approach for Identification and Quantification of C-Terminal Peptides: Incorporation of Isotopic Arginine Labeling Based on Oxazolone Chemistry. Anal Chem 2013; 85:10745-53. [DOI: 10.1021/ac401647m] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Minbo Liu
- Shanghai
Cancer Centre and Department of Chemistry, Fudan University, Shanghai 200032, P. R. China
| | - Lijuan Zhang
- Institutes
of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China
| | - Lei Zhang
- Institutes
of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China
| | - Jun Yao
- Institutes
of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China
| | - Pengyuan Yang
- Shanghai
Cancer Centre and Department of Chemistry, Fudan University, Shanghai 200032, P. R. China
- Institutes
of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China
| | - Haojie Lu
- Shanghai
Cancer Centre and Department of Chemistry, Fudan University, Shanghai 200032, P. R. China
- Institutes
of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China
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12
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Richards AL, Vincent CE, Guthals A, Rose CM, Westphall MS, Bandeira N, Coon JJ. Neutron-encoded signatures enable product ion annotation from tandem mass spectra. Mol Cell Proteomics 2013; 12:3812-23. [PMID: 24043425 DOI: 10.1074/mcp.m113.028951] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We report the use of neutron-encoded (NeuCode) stable isotope labeling of amino acids in cell culture for the purpose of C-terminal product ion annotation. Two NeuCode labeling isotopologues of lysine, (13)C6(15)N2 and (2)H8, which differ by 36 mDa, were metabolically embedded in a sample proteome, and the resultant labeled proteins were combined, digested, and analyzed via liquid chromatography and mass spectrometry. With MS/MS scan resolving powers of ~50,000 or higher, product ions containing the C terminus (i.e. lysine) appear as a doublet spaced by exactly 36 mDa, whereas N-terminal fragments exist as a single m/z peak. Through theory and experiment, we demonstrate that over 90% of all y-type product ions have detectable doublets. We report on an algorithm that can extract these neutron signatures with high sensitivity and specificity. In other words, of 15,503 y-type product ion peaks, the y-type ion identification algorithm correctly identified 14,552 (93.2%) based on detection of the NeuCode doublet; 6.8% were misclassified (i.e. other ion types that were assigned as y-type products). Searching NeuCode labeled yeast with PepNovo(+) resulted in a 34% increase in correct de novo identifications relative to searching through MS/MS only. We use this tool to simplify spectra prior to database searching, to sort unmatched tandem mass spectra for spectral richness, for correlation of co-fragmented ions to their parent precursor, and for de novo sequence identification.
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Affiliation(s)
- Alicia L Richards
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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Kim JS, Song JS, Kim Y, Park SB, Kim HJ. De novo analysis of protein N-terminal sequence utilizing MALDI signal enhancing derivatization with Br signature. Anal Bioanal Chem 2011; 402:1911-9. [PMID: 22200925 DOI: 10.1007/s00216-011-5642-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/29/2011] [Accepted: 12/06/2011] [Indexed: 11/24/2022]
Abstract
De novo analysis of protein N-terminal sequence is important for identification of N-terminal proteolytic processing such as N-terminal methionine or signal peptide removal, or for the genome annotation of uncharacterized proteins. We introduce a de novo sequencing method of protein N terminus utilizing matrix-assisted laser desorption/ionization (MALDI) signal enhancing picolinamidination with bromine isotopic tag incorporated to the N terminus. The doublet signature of bromine in the tandem mass (MS/MS) spectrum distinguished N-terminal ion series from C-terminal ion series, facilitating de novo N-terminal sequencing of protein. The dual advantage of MALDI signal enhancement by the basic picolinamidine and b-ion selection aided by Br signature is demonstrated using a variety of peptides. The N-terminal sequences of myoglobin and hemoglobin as model proteins were determined by incorporating the Br tag to the N terminus of the proteins and obtaining a series of b-ions with Br signature by MS/MS analysis after chymotryptic digestion of the tagged proteins. The N-terminal peptide was selected for MS/MS analysis from the chymotryptic digest based on the Br signature in the mass spectrum. Identification of phosphorylation site as well as N-terminal sequencing of a phosphopeptide was straightforward.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul 151-742, Republic of Korea.
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14
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Song J, Kim HJ. Matrix-assisted laser desorption/ionization mass spectrometry peptide sequencing utilizing selective N-terminal bromoacetylation. Anal Biochem 2011; 423:269-76. [PMID: 22178914 DOI: 10.1016/j.ab.2011.11.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 10/21/2011] [Accepted: 11/21/2011] [Indexed: 10/14/2022]
Abstract
In tandem mass spectrometric peptide sequencing, simplifying the mass spectrum is often desirable. The b-series ions were distinguished from the y-series ions in the MALDI TOF-TOF spectra by incorporating a bromine-tag to the N-terminal amino group through rapid and selective acetylation using bromoacetic anhydride without blocking the lysine and tyrosine residues. The 51:49 ratio of Br-79 and Br-81 isotopes facilitated identification of ions carrying the tag. With the Br-tag in the b-series ions, N-terminal sequencing of tryptic peptides from hemoglobin as well as model peptides was straightforward. When the b-ions were low in intensity, ions without the Br-tag were identified as y-ions and used for sequencing.
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Affiliation(s)
- Jinsu Song
- Department of Chemistry, Seoul National University, Seoul, Republic of Korea
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