1
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Liu XR, Zhang MM, Gross ML. Mass Spectrometry-Based Protein Footprinting for Higher-Order Structure Analysis: Fundamentals and Applications. Chem Rev 2020; 120:4355-4454. [PMID: 32319757 PMCID: PMC7531764 DOI: 10.1021/acs.chemrev.9b00815] [Citation(s) in RCA: 130] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Proteins adopt different higher-order structures (HOS) to enable their unique biological functions. Understanding the complexities of protein higher-order structures and dynamics requires integrated approaches, where mass spectrometry (MS) is now positioned to play a key role. One of those approaches is protein footprinting. Although the initial demonstration of footprinting was for the HOS determination of protein/nucleic acid binding, the concept was later adapted to MS-based protein HOS analysis, through which different covalent labeling approaches "mark" the solvent accessible surface area (SASA) of proteins to reflect protein HOS. Hydrogen-deuterium exchange (HDX), where deuterium in D2O replaces hydrogen of the backbone amides, is the most common example of footprinting. Its advantage is that the footprint reflects SASA and hydrogen bonding, whereas one drawback is the labeling is reversible. Another example of footprinting is slow irreversible labeling of functional groups on amino acid side chains by targeted reagents with high specificity, probing structural changes at selected sites. A third footprinting approach is by reactions with fast, irreversible labeling species that are highly reactive and footprint broadly several amino acid residue side chains on the time scale of submilliseconds. All of these covalent labeling approaches combine to constitute a problem-solving toolbox that enables mass spectrometry as a valuable tool for HOS elucidation. As there has been a growing need for MS-based protein footprinting in both academia and industry owing to its high throughput capability, prompt availability, and high spatial resolution, we present a summary of the history, descriptions, principles, mechanisms, and applications of these covalent labeling approaches. Moreover, their applications are highlighted according to the biological questions they can answer. This review is intended as a tutorial for MS-based protein HOS elucidation and as a reference for investigators seeking a MS-based tool to address structural questions in protein science.
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Affiliation(s)
| | | | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO, USA, 63130
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2
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Guo C, Steinberg LK, Cheng M, Song JH, Henderson JP, Gross ML. Site-Specific Siderocalin Binding to Ferric and Ferric-Free Enterobactin As Revealed by Mass Spectrometry. ACS Chem Biol 2020; 15:1154-1160. [PMID: 31869199 PMCID: PMC7236765 DOI: 10.1021/acschembio.9b00741] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 12/23/2019] [Indexed: 11/29/2022]
Abstract
Both host and pathogen competitively manipulate coordination environments during bacterial infections. Human cells release the innate immune protein siderocalin (Scn, also known as lipocalin-2/Lcn2, neutrophil gelatinase-associated lipocalin/NGAL) that can inhibit bacterial growth by sequestering iron in a ferric complex with enterobactin (Ent), the ubiquitous Escherichia coli siderophore. Pathogenic E. coli use the virulence-associated esterase IroE to linearize the Ent cyclic trilactone to linear enterobactin (lin-Ent). We characterized lin-Ent interactions with Scn by using native mass spectrometry (MS) with hydrogen-deuterium exchange (HDX) and Lys/Arg specific covalent footprinting. These approaches support 1:1 binding of both Fe(III)-lin-Ent to Scn and iron-free lin-Ent to Scn. Both ferric and nonferric lin-Ent localize to all three pockets of the Scn calyx, consistent with Scn capture of lin-Ent both before and after Fe(III) chelation. These findings raise the possibility that Scn neutralizes both siderophores and siderophore-bound iron during infections. This integrated, MS-based approach circumvents the limitations that frustrate traditional structural approaches to examining Scn interactions with enterobactin-based ligands.
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Affiliation(s)
- Chunyang Guo
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Lindsey K. Steinberg
- Division
of Infectious Diseases, Department of Medicine, the Center for Women’s
Infectious Disease Research, Washington
University School of Medicine, St. Louis, Missouri 63110, United States
| | - Ming Cheng
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Jong Hee Song
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
| | - Jeffrey P. Henderson
- Division
of Infectious Diseases, Department of Medicine, the Center for Women’s
Infectious Disease Research, Washington
University School of Medicine, St. Louis, Missouri 63110, United States
| | - Michael L. Gross
- Department
of Chemistry, Washington University, St. Louis, Missouri 63130, United States
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3
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Zhao B, Reilly CP, Reilly JP. ETD-Cleavable Linker for Confident Cross-linked Peptide Identifications. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1631-1642. [PMID: 31098958 DOI: 10.1007/s13361-019-02227-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 04/12/2019] [Accepted: 04/13/2019] [Indexed: 06/09/2023]
Abstract
Peptide cross-links formed using the homobifunctional-linker diethyl suberthioimidate (DEST) are shown to be ETD-cleavable. DEST has a spacer arm consisting of a 6-carbon alkyl chain and it cleaves at the amidino groups created upon reaction with primary amines. In ETD MS2 spectra, DEST cross-links can be recognized based on mass pairs consisting of peptide-NH2• and peptide+linker+NH3 ions, and backbone cleavages are more equally distributed over the two constituent peptides compared with collisional activation. Dead ends that are often challenging to distinguish from cross-links are diagnosed by intense reporter ions. ETD mass pairs can be used in MS3 experiments to confirm cross-link identifications. These features provide a simple but reliable approach to identify cross-links that should facilitate studies of protein complexes.
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Affiliation(s)
- Bingqing Zhao
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN, 47405, USA
| | - Colin P Reilly
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN, 47405, USA
| | - James P Reilly
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN, 47405, USA.
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4
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Silva CJ, Erickson-Beltran ML, Dynin IC. Covalent Surface Modification of Prions: A Mass Spectrometry-Based Means of Detecting Distinctive Structural Features of Prion Strains. Biochemistry 2016; 55:894-902. [PMID: 26786805 DOI: 10.1021/acs.biochem.5b01068] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prions (PrP(Sc)) are molecular pathogens that are able to convert the isosequential normal cellular prion protein (PrP(C)) into a prion. The only demonstrated difference between PrP(C) and PrP(Sc) is conformational: they are isoforms. A given host can be infected by more than one kind or strain of prion. Five strains of hamster-adapted scrapie [Sc237 (=263K), drowsy, 139H, 22AH, and 22CH] and recombinant PrP were reacted with five different concentrations (0, 1, 5, 10, and 20 mM) of reagent (N-hydroxysuccinimide ester of acetic acid) that acetylates lysines. The extent of lysine acetylation was quantitated by mass spectrometry. The lysines in rPrP react similarly. The lysines in the strains react differently from one another in a given strain and react differently when strains are compared. Lysines in the C-terminal region of prions have different strain-dependent reactivity. The results are consistent with a recently proposed model for the structure of a prion. This model proposes that prions are composed of a four-rung β-solenoid structure comprised of four β-sheets that are joined by loops and turns of amino acids. Variation in the amino acid composition of the loops and β-sheet structures is thought to result in different strains of prions.
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Affiliation(s)
- Christopher J Silva
- Western Regional Research Center, United States Department of Agriculture , Albany, California 94710, United States
| | - Melissa L Erickson-Beltran
- Western Regional Research Center, United States Department of Agriculture , Albany, California 94710, United States
| | - Irina C Dynin
- Western Regional Research Center, United States Department of Agriculture , Albany, California 94710, United States
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5
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Vaughan RC, Kao CC. Mapping protein-RNA interactions by RCAP, RNA-cross-linking and peptide fingerprinting. Methods Mol Biol 2015; 1297:225-236. [PMID: 25896007 DOI: 10.1007/978-1-4939-2562-9_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
RNA nanotechnology often feature protein RNA complexes. The interaction between proteins and large RNAs are difficult to study using traditional structure-based methods like NMR or X-ray crystallography. RCAP, an approach that uses reversible-cross-linking affinity purification method coupled with mass spectrometry, has been developed to map regions within proteins that contact RNA. This chapter details how RCAP is applied to map protein-RNA contacts within virions.
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Affiliation(s)
- Robert C Vaughan
- Department of Molecular and Cellular Biochemistry, Indiana University, 212 S. Hawthorne St., 201A Simon Hall, Bloomington, IN, 47405, USA,
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6
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Cammarata M, Lin KY, Pruet J, Liu HW, Brodbelt J. Probing the Unfolding of Myoglobin and Domain C of PARP-1 with Covalent Labeling and Top-Down Ultraviolet Photodissociation Mass Spectrometry. Anal Chem 2014; 86:2534-42. [DOI: 10.1021/ac4036235] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Michael Cammarata
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Ke-Yi Lin
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Jeff Pruet
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Hung-wen Liu
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Jennifer Brodbelt
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
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7
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O'Brien JP, Mayberry LK, Murphy PA, Browning KS, Brodbelt JS. Evaluating the conformation and binding interface of cap-binding proteins and complexes via ultraviolet photodissociation mass spectrometry. J Proteome Res 2013; 12:5867-77. [PMID: 24200290 DOI: 10.1021/pr400869u] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
We report the structural analysis of cap-binding proteins using a chemical probe/ultraviolet photodissociation (UVPD) mass spectrometry strategy for evaluating solvent accessibility of proteins. Our methodology utilized a chromogenic probe (NN) to probe the exposed amine residues of wheat eukaryotic translation initiation factor 4E (eIF4E), eIF4E in complex with a fragment of eIF4G ("mini-eIF4F"), eIF4E in complex with full length eIF4G, and the plant specific cap-binding protein, eIFiso4E. Structural changes of eIF4E in the absence and presence of excess dithiothreitol and in complex with a fragment of eIF4G or full-length eIF4G are mapped. The results indicate that there are particular lysine residues whose environment changes in the presence of dithiothreitol or eIF4G, suggesting that changes in the structure of eIF4E are occurring. On the basis of the crystal structure of wheat eIF4E and a constructed homology model of the structure for eIFiso4E, the reactivities of lysines in each protein are rationalized. Our results suggest that chemical probe/UVPD mass spectrometry can successfully predict dynamic structural changes in solution that are consistent with known crystal structures. Our findings reveal that the binding of m(7)GTP to eIF4E and eIFiso4E appears to be dependent on the redox state of a pair of cysteines near the m(7)GTP binding site. In addition, tertiary structural changes of eIF4E initiated by the formation of a complex containing a fragment of eIF4G and eIF4E were observed.
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Affiliation(s)
- John P O'Brien
- Department of Chemistry and Biochemistry and ‡Institute for Cell and Molecular Biology, The University of Texas at Austin , 1 University Station A5300, Austin, Texas 78712, United States
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8
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O'Brien JP, Pruet JM, Brodbelt JS. Chromogenic chemical probe for protein structural characterization via ultraviolet photodissociation mass spectrometry. Anal Chem 2013; 85:7391-7. [PMID: 23855605 DOI: 10.1021/ac401305f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A chemical probe/ultraviolet photodissociation (UVPD) mass spectrometry strategy for evaluating structures of proteins and protein complexes is reported, as demonstrated for lysozyme and beta-lactoglobulin with and without bound ligands. The chemical probe, NN, incorporates a UV chromophore that endows peptides with high cross sections at 351 nm, a wavelength not absorbed by unmodified peptides. Thus, NN-modified peptides can readily be differentiated from nonmodified peptides in complex tryptic digests created upon proteolysis of proteins after their exposure to the NN chemical probe. The NN chemical probe also affords two diagnostic reporter ions detected upon UVPD of the NN-modified peptide that provides a facile method for the identification of NN peptides within complex mixtures. Quantitation of the modified and unmodified peptides allows estimation of the surface accessibilities of lysine residues based on their relative reactivities with the NN chemical probe.
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Affiliation(s)
- John P O'Brien
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712, United States
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9
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Lauber MA, Rappsilber J, Reilly JP. Dynamics of ribosomal protein S1 on a bacterial ribosome with cross-linking and mass spectrometry. Mol Cell Proteomics 2012; 11:1965-76. [PMID: 23033476 PMCID: PMC3518124 DOI: 10.1074/mcp.m112.019562] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 09/19/2012] [Indexed: 11/23/2022] Open
Abstract
Ribosomal protein S1 has been shown to be a significant effector of prokaryotic translation. The protein is in fact capable of efficiently initiating translation, regardless of the presence of a Shine-Dalgarno sequence in mRNA. Structural insights into this process have remained elusive, as S1 is recalcitrant to traditional techniques of structural analysis, such as x-ray crystallography. Through the application of protein cross-linking and high resolution mass spectrometry, we have detailed the ribosomal binding site of S1 and have observed evidence of its dynamics. Our results support a previous hypothesis that S1 acts as the mRNA catching arm of the prokaryotic ribosome. We also demonstrate that in solution the major domains of the 30S subunit are remarkably flexible, capable of moving 30-50Å with respect to one another.
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Affiliation(s)
- Matthew A. Lauber
- From the ‡Department of Chemistry, Indiana University, Bloomington, Indiana 47405
| | - Juri Rappsilber
- §Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, UK and Institut für Biotechnologie, Technische Universität Berlin, 13353 Berlin, Germany
| | - James P. Reilly
- From the ‡Department of Chemistry, Indiana University, Bloomington, Indiana 47405
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10
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Jaffee EG, Lauber MA, Running WE, Reilly JP. In Vitro and In Vivo Chemical Labeling of Ribosomal Proteins: A Quantitative Comparison. Anal Chem 2012; 84:9355-61. [DOI: 10.1021/ac302115m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ethan G. Jaffee
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - Matthew A. Lauber
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - William E. Running
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - James P. Reilly
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
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11
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Xu M, Yang L, Wang Q. A Way to Probe the Microenvironment of Free Sulfhydryls in Intact Proteins with a Series of Monofunctional Organic Mercurials. Chemistry 2012; 18:13989-93. [DOI: 10.1002/chem.201200901] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Revised: 08/08/2012] [Indexed: 11/10/2022]
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12
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Vaughan R, Fan B, You JS, Kao CC. Identification and functional characterization of the nascent RNA contacting residues of the hepatitis C virus RNA-dependent RNA polymerase. RNA (NEW YORK, N.Y.) 2012; 18:1541-52. [PMID: 22736798 PMCID: PMC3404374 DOI: 10.1261/rna.031914.111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 05/30/2012] [Indexed: 05/21/2023]
Abstract
Understanding how the hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) interacts with nascent RNA would provide valuable insight into the virus's mechanism for RNA synthesis. Using a peptide mass fingerprinting method and affinity capture of peptides reversibly cross-linked to an alkyn-labeled nascent RNA, we identified a region below the Δ1 loop in the fingers domain of the HCV RdRp that contacts the nascent RNA. A modification protection assay was used to confirm the assignment. Several mutations within the putative nascent RNA binding region were generated and analyzed for RNA synthesis in vitro and in the HCV subgenomic replicon. All mutations tested within this region showed a decrease in primer-dependent RNA synthesis and decreased stabilization of the ternary complex. The results from this study advance our understanding of the structure and function of the HCV RdRp and the requirements for HCV RNA synthesis. In addition, a model of nascent RNA interaction is compared with results from structural studies.
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Affiliation(s)
- Robert Vaughan
- The Biochemistry Interdisciplinary Program, Indiana University, Bloomington, Indiana 47405, USA
| | - Baochang Fan
- The Biochemistry Interdisciplinary Program, Indiana University, Bloomington, Indiana 47405, USA
| | - Jin-Sam You
- Indiana University School of Medicine, IUPUI, Indianapolis, Indiana 46202, USA
| | - C. Cheng Kao
- The Biochemistry Interdisciplinary Program, Indiana University, Bloomington, Indiana 47405, USA
- Corresponding authorE-mail
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13
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Vaughan R, Li Y, Fan B, Ranjith-Kumar CT, Kao CC. RNA binding by the NS3 protease of the hepatitis C virus. Virus Res 2012; 169:80-90. [PMID: 22814430 DOI: 10.1016/j.virusres.2012.07.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 07/08/2012] [Accepted: 07/09/2012] [Indexed: 12/22/2022]
Abstract
The hepatitis C virus (HCV) nonstructural protein 3 (NS3) is essential for the processing of the HCV polyprotein, the replication of HCV RNA, and to short circuit innate immunity signaling. NS3 contains an N-terminal domain with protease activity and a C-terminal domain with helicase activity. The two domains communicate with each other along with other HCV and cellular proteins. Herein we show that RNAs can bind directly to the active site cleft of the NS3 protease domain (NS3P) and inhibit proteolysis of peptide substrates. RNAs that are less apt to form intramolecular structures have a stronger inhibitory activity than RNAs with more stable base paired regions. Two mutations in the protease domain that resulted in decreased affinity to ssRNA were also defective in RNA-induced ATPase activity from the helicase domain of NS3. The coordinated effects on inhibition of protease activity and stimulation of ATPase activity raise the possibility that RNA serves as a regulatory switch for the two processes.
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Affiliation(s)
- Robert Vaughan
- The Biochemistry Interdisciplinary Program, Indiana University, Bloomington, IN 47405, USA
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14
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Running WE, Ni P, Kao CC, Reilly JP. Chemical reactivity of brome mosaic virus capsid protein. J Mol Biol 2012; 423:79-95. [PMID: 22750573 DOI: 10.1016/j.jmb.2012.06.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 12/12/2022]
Abstract
Viral particles are biological machines that have evolved to package, protect, and deliver the viral genome into the host via regulated conformational changes of virions. We have developed a procedure to modify lysine residues with S-methylthioacetimidate across the pH range from 5.5 to 8.5. Lysine residues that are not completely modified are involved in tertiary or quaternary structural interactions, and their extent of modification can be quantified as a function of pH. This procedure was applied to the pH-dependent structural transitions of brome mosaic virus (BMV). As the reaction pH increases from 5.5 to 8.5, the average number of modified lysine residues in the BMV capsid protein increases from 6 to 12, correlating well with the known pH-dependent swelling behavior of BMV virions. The extent of reaction of each of the capsid protein's lysine residues has been quantified at eight pH values using coupled liquid chromatography-tandem mass spectrometry. Each lysine can be assigned to one of three structural classes identified by inspection of the BMV virion crystal structure. Several lysine residues display reactivity that indicates their involvement in dynamic interactions that are not obvious in the crystal structure. The influence of several capsid protein mutants on the pH-dependent structural transition of BMV has also been investigated. Mutant H75Q exhibits an altered swelling transition accompanying solution pH increases. The H75Q capsids show increased reactivity at lysine residues 64 and 130, residues distal from the dimer interface occupied by H75, across the entire pH range.
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Affiliation(s)
- W E Running
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
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15
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Vasicek L, O'Brien JP, Browning KS, Tao Z, Liu HW, Brodbelt JS. Mapping protein surface accessibility via an electron transfer dissociation selectively cleavable hydrazone probe. Mol Cell Proteomics 2012; 11:O111.015826. [PMID: 22393264 DOI: 10.1074/mcp.o111.015826] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A protein's surface influences its role in protein-protein interactions and protein-ligand binding. Mass spectrometry can be used to give low resolution structural information about protein surfaces and conformations when used in combination with derivatization methods that target surface accessible amino acid residues. However, pinpointing the resulting modified peptides upon enzymatic digestion of the surface-modified protein is challenging because of the complexity of the peptide mixture and low abundance of modified peptides. Here a novel hydrazone reagent (NN) is presented that allows facile identification of all modified surface residues through a preferential cleavage upon activation by electron transfer dissociation coupled with a collision activation scan to pinpoint the modified residue in the peptide sequence. Using this approach, the correlation between percent reactivity and surface accessibility is demonstrated for two biologically active proteins, wheat eIF4E and PARP-1 Domain C.
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Affiliation(s)
- Lisa Vasicek
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
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16
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Chang FMJ, Lauber MA, Running WE, Reilly JP, Giedroc DP. Ratiometric pulse-chase amidination mass spectrometry as a probe of biomolecular complex formation. Anal Chem 2011; 83:9092-9. [PMID: 22007758 DOI: 10.1021/ac202154r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Selective chemical modification of protein side chains coupled with mass spectrometry is often most informative when used to compare residue-specific reactivities in a number of functional states or macromolecular complexes. Herein, we develop ratiometric pulse-chase amidination mass spectrometry (rPAm-MS) as a site-specific probe of lysine reactivities at equilibrium using the Cu(I)-sensing repressor CsoR from Bacillus subtilis as a model system. CsoR in various allosteric states was reacted with S-methyl thioacetimidate (SMTA) for pulse time, t, and chased with excess of S-methyl thiopropionimidate (SMTP) (Δ = 14 amu), quenched and digested with chymotrypsin or Glu-C protease, and peptides were quantified by high-resolution matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and/or liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). We show that the reactivities of individual lysines from peptides containing up to three Lys residues are readily quantified using this method. New insights into operator DNA binding and the Cu(I)-mediated structural transition in the tetrameric copper sensor CsoR are also obtained.
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Affiliation(s)
- Feng-Ming James Chang
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405-7102, USA
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17
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Xu Y, Falk IN, Hallen MA, Fitzgerald MC. Mass Spectrometry- and Lysine Amidination-Based Protocol for Thermodynamic Analysis of Protein Folding and Ligand Binding Interactions. Anal Chem 2011; 83:3555-62. [DOI: 10.1021/ac200211t] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ying Xu
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Irene N. Falk
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Mark A. Hallen
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Michael C. Fitzgerald
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
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18
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Lauber MA, Reilly JP. Novel amidinating cross-linker for facilitating analyses of protein structures and interactions. Anal Chem 2011; 82:7736-43. [PMID: 20795639 DOI: 10.1021/ac101586z] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel bifunctional thioimidate cross-linking reagent (diethyl suberthioimidate) that modifies amines without sacrificing their native basicity is developed. Intermolecular cross-linking of neurotensin and intramolecular cross-linking of cytochrome c under physiological conditions is investigated with this reagent. Because it does not perturb the electrostatic properties of a protein, it is unlikely to lead to artifactual conclusions about native protein structure. The interpeptide cross-links formed with this reagent are easily separated from other tryptic fragments using strong cation exchange chromatography, and they have a readily identified mass spectrometric signature. The use of this novel amidinating protein cross-linking reagent holds great promise for efficient, large-scale structural analysis of complex systems.
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Affiliation(s)
- Matthew A Lauber
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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19
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Running WE, Reilly JP. Variation of the chemical reactivity of Thermus thermophilus HB8 ribosomal proteins as a function of pH. Proteomics 2010; 10:3669-87. [DOI: 10.1002/pmic.201000342] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Zhou X, Lu Y, Wang W, Borhan B, Reid GE. 'Fixed charge' chemical derivatization and data dependant multistage tandem mass spectrometry for mapping protein surface residue accessibility. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1339-1351. [PMID: 20452239 DOI: 10.1016/j.jasms.2010.03.047] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Revised: 03/20/2010] [Accepted: 03/20/2010] [Indexed: 05/29/2023]
Abstract
Protein surface accessible residues play an important role in protein folding, protein-protein interactions and protein-ligand binding. However, a common problem associated with the use of selective chemical labeling methods for mapping protein solvent accessible residues is that when a complicated peptide mixture resulting from a large protein or protein complex is analyzed, the modified peptides may be difficult to identify and characterize amongst the largely unmodified peptide population (i.e., the 'needle in a haystack' problem). To address this challenge, we describe here the development of a strategy involving the synthesis and application of a novel 'fixed charge' sulfonium ion containing lysine-specific protein modification reagent, S,S'-dimethylthiobutanoylhydroxysuccinimide ester (DMBNHS), coupled with capillary HPLC-ESI-MS, automated CID-MS/MS, and data-dependant neutral loss mode MS(3) in an ion trap mass spectrometer, to map the surface accessible lysine residues in a small model protein, cellular retinoic acid binding protein II (CRABP II). After reaction with different reagent:protein ratios and digestion with Glu-C, modified peptides are selectively identified and the number of modifications within each peptide are determined by CID-MS/MS, via the exclusive neutral loss(es) of dimethylsulfide, independently of the amino acid composition and precursor ion charge state (i.e., proton mobility) of the peptide. The observation of these characteristic neutral losses are then used to automatically 'trigger' the acquisition of an MS(3) spectrum to allow the peptide sequence and the site(s) of modification to be characterized. Using this approach, the experimentally determined relative solvent accessibilities of the lysine residues were found to show good agreement with the known solution structure of CRABP II.
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Affiliation(s)
- Xiao Zhou
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48842, USA
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21
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Brier S, Pflieger D, Le Mignon M, Bally I, Gaboriaud C, Arlaud GJ, Daniel R. Mapping surface accessibility of the C1r/C1s tetramer by chemical modification and mass spectrometry provides new insights into assembly of the human C1 complex. J Biol Chem 2010; 285:32251-63. [PMID: 20592021 DOI: 10.1074/jbc.m110.149112] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1, the complex that triggers the classic pathway of complement, is a 790-kDa assembly resulting from association of a recognition protein C1q with a Ca(2+)-dependent tetramer comprising two copies of the proteases C1r and C1s. Early structural investigations have shown that the extended C1s-C1r-C1r-C1s tetramer folds into a compact conformation in C1. Recent site-directed mutagenesis studies have identified the C1q-binding sites in C1r and C1s and led to a three-dimensional model of the C1 complex (Bally, I., Rossi, V., Lunardi, T., Thielens, N. M., Gaboriaud, C., and Arlaud, G. J. (2009) J. Biol. Chem. 284, 19340-19348). In this study, we have used a mass spectrometry-based strategy involving a label-free semi-quantitative analysis of protein samples to gain new structural insights into C1 assembly. Using a stable chemical modification, we have compared the accessibility of the lysine residues in the isolated tetramer and in C1. The labeling data account for 51 of the 73 lysine residues of C1r and C1s. They strongly support the hypothesis that both C1s CUB(1)-EGF-CUB(2) interaction domains, which are distant in the free tetramer, associate with each other in the C1 complex. This analysis also provides the first experimental evidence that, in the proenzyme form of C1, the C1s serine protease domain is partly positioned inside the C1q cone and yields precise information about its orientation in the complex. These results provide further structural insights into the architecture of the C1 complex, allowing significant improvement of our current C1 model.
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Affiliation(s)
- Sébastien Brier
- CNRS, UMR 8587, Université d'Evry-Val-d'Essonne, Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Boulevard François Mitterrand, 91025 Evry, France.
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22
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Lauber MA, Running WE, Reilly JP. B. subtilis ribosomal proteins: structural homology and post-translational modifications. J Proteome Res 2009; 8:4193-206. [PMID: 19653700 DOI: 10.1021/pr801114k] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ribosomal proteins of the model gram-positive bacterium B. subtilis 168 were extensively characterized in a proteomic study. Mass spectra of the 52 proteins expected to be constitutive components of the 70S ribosome were recorded. Peptide MS/MS analysis with an average sequence coverage of 85% supported the identification of these proteins and facilitated the unambiguous assignment of post-translational modifications, including the methylation of S7, L11, and L16 and the N-terminal acetylation of S9. In addition, the high degree of structural homology between B. subtilis and other eubacterial ribosomal proteins was demonstrated through chemical labeling with S-methylthioacetimidate. One striking difference from previous characterizations of bacterial ribosomal proteins is that dozens of protein masses were found to be in error and not easily accounted for by post-translational modifications. This, in turn, led us to discover an inordinate number of sequencing errors in the reference genome of B. subtilis 168. We have found that these errors have been corrected in a recently revised version of the genome.
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Affiliation(s)
- Matthew A Lauber
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.
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23
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Hobbs CA, Deterding LJ, Perera L, Bobay BG, Thompson RJ, Darden TA, Cavanagh J, Tomer KB. Structural characterization of the conformational change in calbindin-D28k upon calcium binding using differential surface modification analyzed by mass spectrometry. Biochemistry 2009; 48:8603-14. [PMID: 19658395 DOI: 10.1021/bi900350q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Calbindin-D28k is a calcium binding protein with six EF hand domains. Calbindin-D28k is unique in that it functions as both a calcium buffer and a sensor protein. It is found in many tissues, including brain, pancreas, kidney, and intestine, playing important roles in each. Calbindin-D28k is known to bind four calcium ions and upon calcium binding undergoes a conformational change. The structure of apo calbindin-D28k is in an ordered state, transitioning into a disordered state as calcium is bound. Once fully loaded with four calcium ions, it again takes on an ordered state. The solution structure of disulfide-reduced holo-calbindin-D28k has been determined by NMR, while the structure of apo calbindin-D28k has yet to be determined. Differential surface modification of lysine and histidine residues analyzed by mass spectrometry has been used in this study to identify, for the first time, the specific regions of calbindin-D28k undergoing conformational changes between the holo and apo states. Using differential surface modification in combination with mass spectrometry, EF hands 1 and 4 as well as the linkers before EF hand 1 and the linkers between EF hands 4 and 5 and EF hands 5 and 6 were identified as regions of conformational change between apo and holo calbindin-D28k. Under the experimental conditions employed, EF hands 2 and 6, which are known not to bind calcium, were unaffected in either form. EF hand 2 is highly accessible; however, EF hand 6 was determined not to be surface accessible in either form. Previous research has identified a disulfide bond between cysteines 94 and 100 in the holo state. Until now, it was unknown whether this bond also exists in the apo form. Our data confirm the presence of the disulfide bond between cysteines 94 and 100 in the holo form and indicate that there is predominantly no disulfide bond between these residues in the apoprotein.
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Affiliation(s)
- Carey A Hobbs
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
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24
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Liu X, Reilly JP. Correlating the Chemical Modification of Escherichia coli Ribosomal Proteins with Crystal Structure Data. J Proteome Res 2009; 8:4466-78. [DOI: 10.1021/pr9002382] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xiaohui Liu
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405
| | - James P. Reilly
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47405
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25
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Mendoza VL, Vachet RW. Probing protein structure by amino acid-specific covalent labeling and mass spectrometry. MASS SPECTROMETRY REVIEWS 2009; 28:785-815. [PMID: 19016300 PMCID: PMC2768138 DOI: 10.1002/mas.20203] [Citation(s) in RCA: 270] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
For many years, amino acid-specific covalent labeling has been a valuable tool to study protein structure and protein interactions, especially for systems that are difficult to study by other means. These covalent labeling methods typically map protein structure and interactions by measuring the differential reactivity of amino acid side chains. The reactivity of amino acids in proteins generally depends on the accessibility of the side chain to the reagent, the inherent reactivity of the label and the reactivity of the amino acid side chain. Peptide mass mapping with ESI- or MALDI-MS and peptide sequencing with tandem MS are typically employed to identify modification sites to provide site-specific structural information. In this review, we describe the reagents that are most commonly used in these residue-specific modification reactions, details about the proper use of these covalent labeling reagents, and information about the specific biochemical problems that have been addressed with covalent labeling strategies.
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Affiliation(s)
- Vanessa Leah Mendoza
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA.
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26
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Ahmed KEAM, Chen WQ, John JPP, Kang SU, Lubec G. Complete sequencing of the recombinant granulocyte-colony stimulating factor (filgrastim) and detection of biotinylation by mass spectrometry. Amino Acids 2009; 38:1043-9. [DOI: 10.1007/s00726-009-0312-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 05/30/2009] [Indexed: 10/20/2022]
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27
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Running WE, Reilly JP. Ribosomal Proteins of Deinococcus radiodurans: Their Solvent Accessibility and Reactivity. J Proteome Res 2009; 8:1228-46. [DOI: 10.1021/pr800544y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- William E. Running
- Department of Chemistry, Indiana University, Bloomington, Indiana, 47405
| | - James P. Reilly
- Department of Chemistry, Indiana University, Bloomington, Indiana, 47405
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28
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Pankavich S, Miao Y, Ortoleva J, Shreif Z, Ortoleva P. Stochastic dynamics of bionanosystems: Multiscale analysis and specialized ensembles. J Chem Phys 2008; 128:234908. [PMID: 18570529 PMCID: PMC2671664 DOI: 10.1063/1.2931572] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 04/28/2008] [Indexed: 11/14/2022] Open
Abstract
An approach for simulating bionanosystems such as viruses and ribosomes is presented. This calibration-free approach is based on an all-atom description for bionanosystems, a universal interatomic force field, and a multiscale perspective. The supramillion-atom nature of these bionanosystems prohibits the use of a direct molecular dynamics approach for phenomena such as viral structural transitions or self-assembly that develop over milliseconds or longer. A key element of these multiscale systems is the cross-talk between, and consequent strong coupling of processes over many scales in space and time. Thus, overall nanoscale features of these systems control the relative probability of atomistic fluctuations, while the latter mediate the average forces and diffusion coefficients that induce the dynamics of these nanoscale features. This feedback loop is overlooked in typical coarse-grained methods. We elucidate the role of interscale cross-talk and overcome bionanosystem simulation difficulties with (1) automated construction of order parameters (OPs) describing suprananometer scale structural features, (2) construction of OP-dependent ensembles describing the statistical properties of atomistic variables that ultimately contribute to the entropies driving the dynamics of the OPs, and (3) the derivation of a rigorous equation for the stochastic dynamics of the OPs. As the OPs capture hydrodynamic modes in the host medium, "long-time tails" in the correlation functions yielding the generalized diffusion coefficients do not emerge. Since the atomic-scale features of the system are treated statistically, several ensembles are constructed that reflect various experimental conditions. Attention is paid to the proper use of the Gibbs hypothesized equivalence of long-time and ensemble averages to accommodate the varying experimental conditions. The theory provides a basis for a practical, quantitative bionanosystem modeling approach that preserves the cross-talk between the atomic and nanoscale features. A method for integrating information from nanotechnical experimental data in the derivation of equations of stochastic OP dynamics is also introduced.
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Affiliation(s)
- S Pankavich
- Department of Mathematics, Indiana University, Bloomington, Indiana 47405, USA
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29
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Mingels AM, van Dongen JL, Merkx M. Mapping preferred sites for fluorescent labeling by combining fluorescence and MS analysis of tryptic CNA35 protein digests. J Chromatogr B Analyt Technol Biomed Life Sci 2008; 863:293-7. [DOI: 10.1016/j.jchromb.2007.12.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 12/11/2007] [Accepted: 12/24/2007] [Indexed: 11/17/2022]
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30
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Kim JS, Kim JH, Kim HJ. Matrix-assisted laser desorption/ionization signal enhancement of peptides by picolinamidination of amino groups. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:495-502. [PMID: 18205249 DOI: 10.1002/rcm.3392] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Picolinamidination of amino groups in peptides was carried out using ethyl picolinimidate tetrafluoroborate synthesized from picolinamide and triethyloxonium tetrafluoroborate. The N-terminal amino group as well as the epsilon-amino group of lysine were derivatized. The matrix-assisted laser desorption/ionization (MALDI) signal of a peptide was enhanced 20-35-fold upon picolinamidination depending on the number of amino groups derivatized. The signal enhancement effect is much higher than that of acetamidination or guanidination previously reported. Improved protein identification by mass mapping of the derivatized peptides was demonstrated.
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Affiliation(s)
- Jong-Seo Kim
- Department of Chemistry, Seoul National University, Seoul, Korea 151-747
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31
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Chen H, Schuster MC, Sfyroera G, Geisbrecht BV, Lambris JD. Solution insights into the structure of the Efb/C3 complement inhibitory complex as revealed by lysine acetylation and mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:55-65. [PMID: 18293486 PMCID: PMC2775528 DOI: 10.1016/j.jasms.2007.10.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The extracellular fibrinogen-binding protein (Efb), an immunosuppressive and anti-inflammatory protein secreted by Staphylococcus aureus, has been identified as a potent inhibitor of complement-mediated innate immunity. Efb functions by binding to and disrupting the function of complement component 3 (C3). In a recent study, we presented a high-resolution co-crystal structure of the complement inhibitory domain of Efb (Efb-C) bound to its cognate domain (C3d) from human C3 and employed a series of structure/function analyses that provided evidence for an entirely new, conformational change-based mechanism of complement inhibition. To better understand the Efb/C3 complex and its downstream effects on C3 inhibition, we investigated the solvent-accessibility and protein interface of Efb(-C)/C3d using a method of lysine acetylation, proteolytic digestion, and mass spectrometric analysis. Lysine modification in Efb was monitored by the mass increment of lysine-containing fragments. Besides confirming the binding sites observed in co-crystal structure study, the in-solution data presented here suggest additional contacting point(s) between the proteins that were not revealed by crystallography. The results of this study demonstrate that solution-based analysis of protein-protein interactions can provide important complementary information on the nature of protein-protein interactions.
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Affiliation(s)
- Hui Chen
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - Michael C. Schuster
- Department of Medicine, Division of Rheumatology University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - Georgia Sfyroera
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - Brian V. Geisbrecht
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, MO 64110
| | - John D. Lambris
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, 19104 USA
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32
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Beardsley RL, Running WE, Reilly JP. Probing the structure of the Caulobacter crescentus ribosome with chemical labeling and mass spectrometry. J Proteome Res 2007; 5:2935-46. [PMID: 17081045 DOI: 10.1021/pr060170w] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ribosomal proteins of Caulobacter crescentus were amidinated before and after disassembly of the organelle and the results analyzed by mass spectrometry. Comparison with structural information from previous X-ray crystal studies of other bacterial ribosomes provides insight about the C. crescentus ribosome. In total, 47 of the 54 proteins present in the ribosome of C. crescentus were detected after labeling. The extent of derivatization for each protein is strongly dependent on the solvent accessibility of its target residues. Proteins of the ribosome stalk, which are known to be largely solvent-accessible, were labeled quite extensively. In striking contrast, other proteins that are known to be highly shielded in their subunits were labeled at very few of their potential sites. Furthermore, evidence that protein L12 binds to the ribosome via its N-terminal domain is consistent with previous findings.
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Affiliation(s)
- Richard L Beardsley
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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33
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Scholten A, Visser NFC, van den Heuvel RHH, Heck AJR. Analysis of protein-protein interaction surfaces using a combination of efficient lysine acetylation and nanoLC-MALDI-MS/MS applied to the E9:Im9 bacteriotoxin--immunity protein complex. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:983-994. [PMID: 16713291 DOI: 10.1016/j.jasms.2006.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 03/13/2006] [Accepted: 03/13/2006] [Indexed: 05/09/2023]
Abstract
To understand how proteins perform their function, knowledge about their structure and dynamics is essential. Here we use a combination of an efficient chemical lysine acetylation reaction and nanoLC-MALDI tandem mass spectrometry to probe the accessibility of every lysine residue in a protein complex. To demonstrate the applicability of this approach, we studied the interaction between the DNase domain of Colicin E9 (E9) and its immunity protein Im9. Free E9 and E9 in complex with Im9 were rapidly acetylated, followed by proteolytic digestion and analysis by LC-MALDI-TOF/TOF MS/MS. Acetylated peptides could be filtered out of the complex peptide mixtures using selective ion chromatograms of the specific immonium marker ions. Additionally, isobaric acetylated peptides, acetylated at different sites, could be separated by their LC retention times. The combination of LC and MALDI-TOF/TOF MS/MS provided information about the amount of acetylation on each individual lysine even for peptides containing several lysine residues. In general, our data agree well with those derived from the crystal structure of E9 and the E9:Im9 complex. Interestingly, next to in the binding interface expected lysines, K89 and K97, two from the crystal structure data unexpected lysines, K81 and K76, were observed to become less exposed upon Im9 binding. Moreover, K55 and K63, positioned in the predicted DNA binding region, were also found to be less accessible upon Im9 binding. These findings may illustrate some of the described differences in the solution-phase structure of the E9:Im9 complex compared with the crystal structure.
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Affiliation(s)
- Arjen Scholten
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA, Utrecht, The Netherlands
| | - Natasja F C Visser
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA, Utrecht, The Netherlands
| | - Robert H H van den Heuvel
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA, Utrecht, The Netherlands
| | - Albert J R Heck
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA, Utrecht, The Netherlands.
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