1
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Polák M, Černý J, Novák P. Isotopic Depletion Increases the Spatial Resolution of FPOP Top-Down Mass Spectrometry Analysis. Anal Chem 2024; 96:1478-1487. [PMID: 38226459 PMCID: PMC10831798 DOI: 10.1021/acs.analchem.3c03759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 11/08/2023] [Accepted: 12/15/2023] [Indexed: 01/17/2024]
Abstract
Protein radical labeling, like fast photochemical oxidation of proteins (FPOP), coupled to a top-down mass spectrometry (MS) analysis offers an alternative analytical method for probing protein structure or protein interaction with other biomolecules, for instance, proteins and DNA. However, with the increasing mass of studied analytes, the MS/MS spectra become complex and exhibit a low signal-to-noise ratio. Nevertheless, these difficulties may be overcome by protein isotope depletion. Thus, we aimed to use protein isotope depletion to analyze FPOP-oxidized samples by top-down MS analysis. For this purpose, we prepared isotopically natural (IN) and depleted (ID) forms of the FOXO4 DNA binding domain (FOXO4-DBD) and studied the protein-DNA interaction interface with double-stranded DNA, the insulin response element (IRE), after exposing the complex to hydroxyl radicals. As shown by comparing tandem mass spectra of natural and depleted proteins, the ID form increased the signal-to-noise ratio of useful fragment ions, thereby enhancing the sequence coverage by more than 19%. This improvement in the detection of fragment ions enabled us to detect 22 more oxidized residues in the ID samples than in the IN sample. Moreover, less common modifications were detected in the ID sample, including the formation of ketones and lysine carbonylation. Given the higher quality of ID top-down MSMS data set, these results provide more detailed information on the complex formation between transcription factors and DNA-response elements. Therefore, our study highlights the benefits of isotopic depletion for quantitative top-down proteomics. Data are available via ProteomeXchange with the identifier PXD044447.
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Affiliation(s)
- Marek Polák
- Institute
of Microbiology of the Czech Academy of Sciences, 14220 Prague, Czech Republic
- Department
of Biochemistry, Faculty of Science, Charles
University, 12843 Prague, Czech Republic
| | - Jiří Černý
- Laboratory
of Structural Bioinformatics of Proteins, Institute of Biotechnology of the Czech Academy of Sciences, 14220 Prague, Czech Republic
| | - Petr Novák
- Institute
of Microbiology of the Czech Academy of Sciences, 14220 Prague, Czech Republic
- Department
of Biochemistry, Faculty of Science, Charles
University, 12843 Prague, Czech Republic
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2
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Cornwell O, Ault JR. Fast photochemical oxidation of proteins coupled with mass spectrometry. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140829. [PMID: 35933084 DOI: 10.1016/j.bbapap.2022.140829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 07/17/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
Fast photochemical oxidation of proteins (FPOP) is a hydroxyl radical footprinting approach whereby radicals, produced by UV laser photolysis of hydrogen peroxide, induce oxidation of amino acid side-chains. Mass Spectrometry (MS) is employed to locate and quantify the resulting irreversible, covalent oxidations to use as a surrogate for side-chain solvent accessibility. Modulation of oxidation levels under different conditions allows for the characterisation of protein conformation, dynamics and binding epitopes. FPOP has been applied to structurally diverse and biopharmaceutically relevant systems from small, monomeric aggregation-prone proteins to proteome-wide analysis of whole organisms. This review evaluates the current state of FPOP, the progress needed to address data analysis bottlenecks, particularly for residue-level analysis, and highlights significant developments of the FPOP platform that have enabled its versatility and complementarity to other structural biology techniques.
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Affiliation(s)
- Owen Cornwell
- Waters Corporation, Stamford Avenue, Altrincham Road, Wilmslow SK9 4AX, UK
| | - James R Ault
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
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3
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Dafun AS, Marcoux J. Structural mass spectrometry of membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140813. [PMID: 35750312 DOI: 10.1016/j.bbapap.2022.140813] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/10/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
The analysis of proteins and protein complexes by mass spectrometry (MS) has come a long way since the invention of electrospray ionization (ESI) in the mid 80s. Originally used to characterize small soluble polypeptide chains, MS has progressively evolved over the past 3 decades towards the analysis of samples of ever increasing heterogeneity and complexity, while the instruments have become more and more sensitive and resolutive. The proofs of concepts and first examples of most structural MS methods appeared in the early 90s. However, their application to membrane proteins, key targets in the biopharma industry, is more recent. Nowadays, a wealth of information can be gathered from such MS-based methods, on all aspects of membrane protein structure: sequencing (and more precisely proteoform characterization), but also stoichiometry, non-covalent ligand binding (metals, drug, lipids, carbohydrates), conformations, dynamics and distance restraints for modelling. In this review, we present the concept and some historical and more recent applications on membrane proteins, for the major structural MS methods.
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Affiliation(s)
- Angelique Sanchez Dafun
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Julien Marcoux
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, UPS, Toulouse, France.
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4
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Das S, Bhatia R. Liquid extraction surface analysis-mass spectrometry: An advanced and environment-friendly analytical tool in modern analysis. J Sep Sci 2022; 45:2746-2765. [PMID: 35579471 DOI: 10.1002/jssc.202100996] [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: 12/17/2021] [Revised: 04/23/2022] [Accepted: 05/10/2022] [Indexed: 11/12/2022]
Abstract
The Liquid Extraction Surface Analysis technique is a new high-throughput instrument for ambient mass spectrometry. The benefits of the Liquid Extraction Surface Analysis-Mass Spectrometry approach are the high throughput screening of samples and the absence of sample preparation. Liquid Extraction Surface Analysis-Mass Spectrometry also consumes less solvent for extraction, making it more environmentally friendly and there is no substrate restriction. It utilizes advanced instrumentation like the use of robotic pipettes, nanoelectrospray systems, electronspray ionization chips which makes it highly efficient. In recent years, Liquid Extraction Surface Analysis-Mass Spectrometry has seen widespread use in a variety of analytical fields including drug metabolite analysis, mapping drug distribution in tissues, protein and lipid characterization etc. In this review, we have summarized the basic working principles of the Liquid Extraction Surface Analysis-Mass Spectrometry approach in detail along with a detailed description of the recently reported applications in the analysis of proteins, lipids, drugs and foods. The investigated analytes along with detection methodologies and significant outcomes of various research reports have been presented with the help of tables. This tool has also been utilized in clinical investigations of biological fluids, fingerprint analysis and authentication of agarwood. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Shibam Das
- Department of Pharmaceutical Chemistry & Analysis, ISF College of Pharmacy Moga, Punjab, 142001, India
| | - Rohit Bhatia
- Department of Pharmaceutical Chemistry & Analysis, ISF College of Pharmacy Moga, Punjab, 142001, India
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5
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Sun J, Li W, Gross ML. Advances in mass spectrometry-based footprinting of membrane proteins. Proteomics 2022; 22:e2100222. [PMID: 35290716 PMCID: PMC10493193 DOI: 10.1002/pmic.202100222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/09/2022]
Abstract
Structural biology is entering an exciting time where many new high-resolution structures of large complexes and membrane proteins (MPs) are determined regularly. These advances have been driven by over 15 years of technological improvements, first in macromolecular crystallography, and recently in cryo-electron microscopy. Obtaining information about MP higher order structure and interactions is also a frontier, important but challenging owing to their unique properties and the need to choose suitable detergents/lipids for their study. The development of mass spectrometry (MS), both instruments and methodology in the past 10 years, has also advanced it as a complementary method to study MP structure and interactions. In this review, we discuss advances in MS-based footprinting for MPs and highlight recent methodologies that offer new promise for MP study by chemical footprinting and mass spectrometry.
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Affiliation(s)
- Jie Sun
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Weikai Li
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
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6
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Pan X, Vachet RW. MEMBRANE PROTEIN STRUCTURES AND INTERACTIONS FROM COVALENT LABELING COUPLED WITH MASS SPECTROMETRY. MASS SPECTROMETRY REVIEWS 2022; 41:51-69. [PMID: 33145813 PMCID: PMC8093322 DOI: 10.1002/mas.21667] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/15/2020] [Accepted: 10/16/2020] [Indexed: 05/31/2023]
Abstract
Membrane proteins are incredibly important biomolecules because they mediate interactions between a cell's external and internal environment. Obtaining information about membrane protein structure and interactions is thus important for understanding these essential biomolecules. Compared with the analyses of water-soluble proteins, the structural analysis of membrane proteins is more challenging owing to their unique chemical properties and the presence of lipid components that are necessary to solubilize them. The combination of covalent labeling (CL) and mass spectrometry (MS) has recently been applied with great success to study membrane protein structure and interactions. These studies have demonstrated the many advantages that CL-MS methods have over other traditional biophysical techniques. In this review, we discuss both amino acid-specific and non-specific labeling approaches and the special considerations needed to address the unique challenges associated with interrogating membrane proteins. This review highlights the aspects of this approach that require special care to be applied correctly and provides a comprehensive review of the membrane protein systems that have been studied by CL-MS. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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7
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Sun J, Liu XR, Li S, He P, Li W, Gross ML. Nanoparticles and photochemistry for native-like transmembrane protein footprinting. Nat Commun 2021; 12:7270. [PMID: 34907205 PMCID: PMC8671412 DOI: 10.1038/s41467-021-27588-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 10/05/2021] [Indexed: 11/29/2022] Open
Abstract
Mass spectrometry-based footprinting can probe higher order structure of soluble proteins in their native states and serve as a complement to high-resolution approaches. Traditional footprinting approaches, however, are hampered for integral membrane proteins because their transmembrane regions are not accessible to solvent, and they contain hydrophobic residues that are generally unreactive with most chemical reagents. To address this limitation, we bond photocatalytic titanium dioxide (TiO2) nanoparticles to a lipid bilayer. Upon laser irradiation, the nanoparticles produce local concentrations of radicals that penetrate the lipid layer, which is made permeable by a simultaneous laser-initiated Paternò-Büchi reaction. This approach achieves footprinting for integral membrane proteins in liposomes, helps locate both ligand-binding residues in a transporter and ligand-induced conformational changes, and reveals structural aspects of proteins at the flexible unbound state. Overall, this approach proves effective in intramembrane footprinting and forges a connection between material science and biology.
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Affiliation(s)
- Jie Sun
- grid.4367.60000 0001 2355 7002Department of Chemistry, Washington University in St. Louis, One Brookings Drive, Box 1134, Saint Louis, MO 63130 USA
| | - Xiaoran Roger Liu
- grid.4367.60000 0001 2355 7002Department of Chemistry, Washington University in St. Louis, One Brookings Drive, Box 1134, Saint Louis, MO 63130 USA
| | - Shuang Li
- grid.4367.60000 0001 2355 7002Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave, Box 8231, St. Louis, MO 63110 USA
| | - Peng He
- grid.4367.60000 0001 2355 7002Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave, Box 8231, St. Louis, MO 63110 USA
| | - Weikai Li
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave, Box 8231, St. Louis, MO, 63110, USA.
| | - Michael L. Gross
- grid.4367.60000 0001 2355 7002Department of Chemistry, Washington University in St. Louis, One Brookings Drive, Box 1134, Saint Louis, MO 63130 USA
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8
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McKenzie-Coe A, Montes NS, Jones LM. Hydroxyl Radical Protein Footprinting: A Mass Spectrometry-Based Structural Method for Studying the Higher Order Structure of Proteins. Chem Rev 2021; 122:7532-7561. [PMID: 34633178 DOI: 10.1021/acs.chemrev.1c00432] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hydroxyl radical protein footprinting (HRPF) coupled to mass spectrometry has been successfully used to investigate a plethora of protein-related questions. The method, which utilizes hydroxyl radicals to oxidatively modify solvent-accessible amino acids, can inform on protein interaction sites and regions of conformational change. Hydroxyl radical-based footprinting was originally developed to study nucleic acids, but coupling the method with mass spectrometry has enabled the study of proteins. The method has undergone several advancements since its inception that have increased its utility for more varied applications such as protein folding and the study of biotherapeutics. In addition, recent innovations have led to the study of increasingly complex systems including cell lysates and intact cells. Technological advances have also increased throughput and allowed for better control of experimental conditions. In this review, we provide a brief history of the field of HRPF and detail recent innovations and applications in the field.
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Affiliation(s)
- Alan McKenzie-Coe
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, United States
| | - Nicholas S Montes
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, United States
| | - Lisa M Jones
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, United States
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9
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Lento C, Wilson DJ. Subsecond Time-Resolved Mass Spectrometry in Dynamic Structural Biology. Chem Rev 2021; 122:7624-7646. [PMID: 34324314 DOI: 10.1021/acs.chemrev.1c00222] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Life at the molecular level is a dynamic world, where the key players-proteins, oligonucleotides, lipids, and carbohydrates-are in a perpetual state of structural flux, shifting rapidly between local minima on their conformational free energy landscapes. The techniques of classical structural biology, X-ray crystallography, structural NMR, and cryo-electron microscopy (cryo-EM), while capable of extraordinary structural resolution, are innately ill-suited to characterize biomolecules in their dynamically active states. Subsecond time-resolved mass spectrometry (MS) provides a unique window into the dynamic world of biological macromolecules, offering the capacity to directly monitor biochemical processes and conformational shifts with a structural dimension provided by the electrospray charge-state distribution, ion mobility, covalent labeling, or hydrogen-deuterium exchange. Over the past two decades, this suite of techniques has provided important insights into the inherently dynamic processes that drive function and pathogenesis in biological macromolecules, including (mis)folding, complexation, aggregation, ligand binding, and enzyme catalysis, among others. This Review provides a comprehensive account of subsecond time-resolved MS and the advances it has enabled in dynamic structural biology, with an emphasis on insights into the dynamic drivers of protein function.
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Affiliation(s)
- Cristina Lento
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
| | - Derek J Wilson
- Department of Chemistry, York University, Toronto, Ontario M3J 1P3, Canada
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10
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Chavez JD, Wippel HH, Tang X, Keller A, Bruce JE. In-Cell Labeling and Mass Spectrometry for Systems-Level Structural Biology. Chem Rev 2021; 122:7647-7689. [PMID: 34232610 PMCID: PMC8966414 DOI: 10.1021/acs.chemrev.1c00223] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Biological systems have evolved to utilize proteins to accomplish nearly all functional roles needed to sustain life. A majority of biological functions occur within the crowded environment inside cells and subcellular compartments where proteins exist in a densely packed complex network of protein-protein interactions. The structural biology field has experienced a renaissance with recent advances in crystallography, NMR, and CryoEM that now produce stunning models of large and complex structures previously unimaginable. Nevertheless, measurements of such structural detail within cellular environments remain elusive. This review will highlight how advances in mass spectrometry, chemical labeling, and informatics capabilities are merging to provide structural insights on proteins, complexes, and networks that exist inside cells. Because of the molecular detection specificity provided by mass spectrometry and proteomics, these approaches provide systems-level information that not only benefits from conventional structural analysis, but also is highly complementary. Although far from comprehensive in their current form, these approaches are currently providing systems structural biology information that can uniquely reveal how conformations and interactions involving many proteins change inside cells with perturbations such as disease, drug treatment, or phenotypic differences. With continued advancements and more widespread adaptation, systems structural biology based on in-cell labeling and mass spectrometry will provide an even greater wealth of structural knowledge.
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Affiliation(s)
- Juan D Chavez
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Helisa H Wippel
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Xiaoting Tang
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - Andrew Keller
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
| | - James E Bruce
- Department of Genome Sciences, University of Washington, Seattle, Washington 98109, United States
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11
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Cornwell O, Ault JR, Bond NJ, Radford SE, Ashcroft AE. Investigation of D76N β 2-Microglobulin Using Protein Footprinting and Structural Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1583-1592. [PMID: 33586970 PMCID: PMC9282677 DOI: 10.1021/jasms.0c00438] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
NMR studies and X-ray crystallography have shown that the structures of the 99-residue amyloidogenic protein β2-microglobulin (β2m) and its more aggregation-prone variant, D76N, are indistinguishable, and hence, the reason for the striking difference in their aggregation propensities remains elusive. Here, we have employed two protein footprinting methods, hydrogen-deuterium exchange (HDX) and fast photochemical oxidation of proteins (FPOP), in conjunction with ion mobility-mass spectrometry, to probe the differences in conformational dynamics of the two proteins. Using HDX-MS, a clear difference in HDX protection is observed between these two proteins in the E-F loop (residues 70-77) which contains the D76N substitution, with a significantly higher deuterium uptake being observed in the variant protein. Conversely, following FPOP-MS only minimal differences in the level of oxidation between the two proteins are observed in the E-F loop region, suggesting only modest side-chain movements in that area. Together the HDX-MS and FPOP-MS data suggest that a tangible perturbation to the hydrogen-bonding network in the E-F loop has taken place in the D76N variant and furthermore illustrate the benefit of using multiple complementary footprinting methods to address subtle, but possibly biologically important, differences between highly similar proteins.
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Affiliation(s)
- Owen Cornwell
- Biopharmaceuticals
R & D, AstraZeneca, Granta Park, Cambridge CB21 6GP, U.K.
| | - James R. Ault
- Astbury
Centre for Structural Molecular Biology & School of Molecular
and Cellular Biology, University of Leeds, Leeds LS2 9JT, U.K.
| | - Nicholas J. Bond
- Biopharmaceuticals
R & D, AstraZeneca, Granta Park, Cambridge CB21 6GP, U.K.
| | - Sheena E. Radford
- Astbury
Centre for Structural Molecular Biology & School of Molecular
and Cellular Biology, University of Leeds, Leeds LS2 9JT, U.K.
| | - Alison E. Ashcroft
- Astbury
Centre for Structural Molecular Biology & School of Molecular
and Cellular Biology, University of Leeds, Leeds LS2 9JT, U.K.
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12
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Cheng Z, Mobley C, Misra SK, Gadepalli RS, Hammond RI, Brown LS, Rimoldi JM, Sharp JS. Self-Organized Amphiphiles Are Poor Hydroxyl Radical Scavengers in Fast Photochemical Oxidation of Proteins Experiments. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1155-1161. [PMID: 33881849 PMCID: PMC8790760 DOI: 10.1021/jasms.0c00457] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Analysis of membrane protein topography using fast photochemical oxidation of proteins (FPOP) has been reported in recent years but is still underrepresented in literature. Based on the hydroxyl radical reactivity of lipids and other amphiphiles, it is believed that the membrane environment acts as a hydroxyl radical scavenger decreasing effective hydroxyl radical doses and resulting in less observed oxidation of proteins. We found no significant change in bulk solvent radical scavenging activity upon the addition of disrupted cellular membranes up to 25600 cells/μL using an inline radical dosimeter. We confirmed the nonscavenging nature of the membrane in bulk solution with the FPOP results of a soluble model protein in the presence of cell membranes, which showed no significant difference in oxidation with or without membranes. The use of detergents revealed that, while soluble detergent below the critical micelle concentration is a potent hydroxyl radical scavenger, additional detergent has little to no hydroxyl radical scavenging effect once the critical micelle concentration is reached. Examination of both an extracellular peptide of the integral membrane protein bacteriorhodopsin as well as a novel hydroxyl radical dosimeter tethered to a Triton X-series amphiphile indicate that proximity to the membrane surface greatly decreases reaction with hydroxyl radicals, even though the oxidation target is equally solvent accessible. These results suggest that the observed reduced oxidation of solvent-accessible surfaces of integral membrane proteins is due to the high local concentration of radical scavengers in the membrane or membrane mimetics competing for the local concentration of hydroxyl radicals.
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Affiliation(s)
- Zhi Cheng
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Charles Mobley
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Sandeep K. Misra
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Rama S. Gadepalli
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Rachel I. Hammond
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Leonid S. Brown
- Department of Physics and Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - John M. Rimoldi
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
| | - Joshua S. Sharp
- Department of Biomolecular Sciences, University of Mississippi, University, MS 38677
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677
- GenNext Technologies, Inc. Half Moon Bay, CA 94019
- Correspondence to
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13
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Tadi S, Misra SK, Sharp JS. Inline Liquid Chromatography-Fast Photochemical Oxidation of Proteins for Targeted Structural Analysis of Conformationally Heterogeneous Mixtures. Anal Chem 2021; 93:3510-3516. [PMID: 33560821 DOI: 10.1021/acs.analchem.0c04872] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Structural analysis of proteins in a conformationally heterogeneous mixture has long been a difficult problem in structural biology. In structural analysis by covalent labeling mass spectrometry, conformational heterogeneity results in data reflecting a weighted average of all conformers, complicating data analysis and potentially causing misinterpretation of results. Here, we describe a method coupling size-exclusion chromatography (SEC) with hydroxyl radical protein footprinting using inline fast photochemical oxidation of proteins (FPOP). Using a controlled synthetic mixture of holomyoglobin and apomyoglobin, we validate that we can achieve accurate footprints of each conformer using LC-FPOP when compared to offline FPOP of each pure conformer. We then applied LC-FPOP to analyze the adalimumab heat-shock aggregation process. We found that the LC-FPOP footprint of unaggregated adalimumab was consistent with a previously published footprint of the native IgG. The LC-FPOP footprint of the aggregation product indicated that heat-shock aggregation primarily protected the hinge region, suggesting that this region is involved with the heat-shock aggregation process of this molecule. LC-FPOP offers a new method to probe dynamic conformationally heterogeneous mixtures that can be separated by SEC such as biopharmaceutical aggregates and to obtain accurate information on the topography of each conformer.
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Affiliation(s)
| | | | - Joshua S Sharp
- GenNext Technologies, Inc., Half Moon Bay, California 94037, United States
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14
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Johnson DT, Di Stefano LH, Jones LM. Fast photochemical oxidation of proteins (FPOP): A powerful mass spectrometry-based structural proteomics tool. J Biol Chem 2019; 294:11969-11979. [PMID: 31262727 DOI: 10.1074/jbc.rev119.006218] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fast photochemical oxidation of proteins (FPOP) is a MS-based method that has proved useful in studies of protein structures, interactions, conformations, and protein folding. The success of this method relies on the irreversible labeling of solvent-exposed amino acid side chains by hydroxyl radicals. FPOP generates these radicals through laser-induced photolysis of hydrogen peroxide. The data obtained provide residue-level resolution of protein structures and interactions on the microsecond timescale, enabling investigations of fast processes such as protein folding and weak protein-protein interactions. An extensive comparison between FPOP and other footprinting techniques gives insight on their complementarity as well as the robustness of FPOP to provide unique structural information once unattainable. The versatility of this method is evidenced by both the heterogeneity of samples that can be analyzed by FPOP and the myriad of applications for which the method has been successfully used: from proteins of varying size to intact cells. This review discusses the wide applications of this technique and highlights its high potential. Applications including, but not limited to, protein folding, membrane proteins, structure elucidation, and epitope mapping are showcased. Furthermore, the use of FPOP has been extended to probing proteins in cells and in vivo These promising developments are also presented herein.
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Affiliation(s)
- Danté T Johnson
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201
| | - Luciano H Di Stefano
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201
| | - Lisa M Jones
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201.
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15
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Sharp JS, Misra SK, Persoff JJ, Egan RW, Weinberger SR. Real Time Normalization of Fast Photochemical Oxidation of Proteins Experiments by Inline Adenine Radical Dosimetry. Anal Chem 2018; 90:12625-12630. [PMID: 30290117 PMCID: PMC7811273 DOI: 10.1021/acs.analchem.8b02787] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hydroxyl radical protein footprinting (HRPF) is a powerful method for measuring protein topography, allowing researchers to monitor events that alter the solvent accessible surface of a protein (e.g., ligand binding, aggregation, conformational changes, etc.) by measuring changes in the apparent rate of reaction of portions of the protein to hydroxyl radicals diffusing in solution. Fast Photochemical Oxidation of Proteins (FPOP) offers an ultrafast benchtop method for radical generation for HRPF, photolyzing hydrogen peroxide using a UV laser to generate high concentrations of hydroxyl radicals that are consumed on roughly a microsecond time scale. The broad reactivity of hydroxyl radicals means that almost anything added to the solution (e.g., ligands, buffers, excipients, etc.) will scavenge hydroxyl radicals, altering their half-life and changing the effective radical concentration experienced by the protein. Similarly, minute changes in peroxide concentration, laser fluence, and buffer composition can alter the effective radical concentration, making reproduction of data challenging. Here, we present a simple method for radical dosimetry that can be carried out as part of the FPOP workflow, allowing for measurement of effective radical concentration in real time. Additionally, by modulating the amount of radical generated, we demonstrate that effective hydroxyl radical yields in FPOP HRPF experiments carried out in buffers with widely differing levels of hydroxyl radical scavenging capacity can be compensated on the fly, yielding statistically indistinguishable results for the same conformer. This method represents a major step in transforming FPOP into a robust and reproducible technology capable of probing protein structure in a wide variety of contexts.
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Affiliation(s)
- Joshua S. Sharp
- Department of BioMolecular Sciences, University of Mississippi, Oxford, MS 38677
- GenNext Technologies, Inc., Montara, CA 94037
| | - Sandeep K. Misra
- Department of BioMolecular Sciences, University of Mississippi, Oxford, MS 38677
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16
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Reading E. Structural Mass Spectrometry of Membrane Proteins within Their Native Lipid Environments. Chemistry 2018; 24:13391-13398. [PMID: 29672954 DOI: 10.1002/chem.201801556] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Indexed: 01/22/2023]
Abstract
Mass spectrometry has emerged as an important structural biology tool for understanding membrane protein structure, function, and dynamics. Generally, structural mass spectrometry of membrane proteins has been performed on purified or reconstituted systems which lack the native lipid membrane and cellular environments. However, there has been progress in the use and adaptations of these methods for probing membrane proteins within increasingly more native contexts. In this Concept article the use and utility of structural mass spectrometry techniques for studying membrane proteins within native environments are highlighted.
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Affiliation(s)
- Eamonn Reading
- Department of Chemistry, King's College London, 7 Trinity Street, SE1 1DB, London, UK
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17
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Chea EE, Jones LM. Analyzing the structure of macromolecules in their native cellular environment using hydroxyl radical footprinting. Analyst 2018; 143:798-807. [DOI: 10.1039/c7an01323j] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hydroxyl radical footprinting (HRF) has been successfully used to study the structure of both nucleic acids and proteins in live cells.
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Affiliation(s)
- Emily E. Chea
- Department of Pharmaceutical Sciences
- University of Maryland
- Baltimore
- USA
| | - Lisa M. Jones
- Department of Pharmaceutical Sciences
- University of Maryland
- Baltimore
- USA
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18
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Manzi L, Barrow AS, Hopper JTS, Kaminska R, Kleanthous C, Robinson CV, Moses JE, Oldham NJ. Carbene Footprinting Reveals Binding Interfaces of a Multimeric Membrane-Spanning Protein. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201708254] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Lucio Manzi
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
| | - Andrew S. Barrow
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
- Current address: La Trobe Institute for Molecular Science; La Trobe University; Melbourne Victoria 3086 Australia
| | - Jonathan T. S. Hopper
- OMass Technologies Ltd.; Centre for Innovation and Enterprise; Begbroke Science Park, Woodstock Road Oxford OX5 1PF UK
| | - Renata Kaminska
- Department of Biochemistry; University of Oxford; South Parks Road Oxford OX1 3QU UK
| | - Colin Kleanthous
- Department of Biochemistry; University of Oxford; South Parks Road Oxford OX1 3QU UK
| | - Carol V. Robinson
- Chemistry Research Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | - John E. Moses
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
- Current address: La Trobe Institute for Molecular Science; La Trobe University; Melbourne Victoria 3086 Australia
| | - Neil J. Oldham
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
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19
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Manzi L, Barrow AS, Hopper JTS, Kaminska R, Kleanthous C, Robinson CV, Moses JE, Oldham NJ. Carbene Footprinting Reveals Binding Interfaces of a Multimeric Membrane-Spanning Protein. Angew Chem Int Ed Engl 2017; 56:14873-14877. [DOI: 10.1002/anie.201708254] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Indexed: 12/28/2022]
Affiliation(s)
- Lucio Manzi
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
| | - Andrew S. Barrow
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
- Current address: La Trobe Institute for Molecular Science; La Trobe University; Melbourne Victoria 3086 Australia
| | - Jonathan T. S. Hopper
- OMass Technologies Ltd.; Centre for Innovation and Enterprise; Begbroke Science Park, Woodstock Road Oxford OX5 1PF UK
| | - Renata Kaminska
- Department of Biochemistry; University of Oxford; South Parks Road Oxford OX1 3QU UK
| | - Colin Kleanthous
- Department of Biochemistry; University of Oxford; South Parks Road Oxford OX1 3QU UK
| | - Carol V. Robinson
- Chemistry Research Laboratory; University of Oxford; South Parks Road Oxford OX1 3QZ UK
| | - John E. Moses
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
- Current address: La Trobe Institute for Molecular Science; La Trobe University; Melbourne Victoria 3086 Australia
| | - Neil J. Oldham
- School of Chemistry; University of Nottingham; University Park Nottingham NG7 2RD UK
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20
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Calabrese AN, Jackson SM, Jones LN, Beckstein O, Heinkel F, Gsponer J, Sharples D, Sans M, Kokkinidou M, Pearson AR, Radford SE, Ashcroft AE, Henderson PJF. Topological Dissection of the Membrane Transport Protein Mhp1 Derived from Cysteine Accessibility and Mass Spectrometry. Anal Chem 2017; 89:8844-8852. [PMID: 28726379 PMCID: PMC5588088 DOI: 10.1021/acs.analchem.7b01310] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Accepted: 07/20/2017] [Indexed: 01/01/2023]
Abstract
Cys accessibility and quantitative intact mass spectrometry (MS) analyses have been devised to study the topological transitions of Mhp1, the membrane protein for sodium-linked transport of hydantoins from Microbacterium liquefaciens. Mhp1 has been crystallized in three forms (outward-facing open, outward-facing occluded with substrate bound, and inward-facing open). We show that one natural cysteine residue, Cys327, out of three, has an enhanced solvent accessibility in the inward-facing (relative to the outward-facing) form. Reaction of the purified protein, in detergent, with the thiol-reactive N-ethylmalemide (NEM), results in modification of Cys327, suggesting that Mhp1 adopts predominantly inward-facing conformations. Addition of either sodium ions or the substrate 5-benzyl-l-hydantoin (L-BH) does not shift this conformational equilibrium, but systematic co-addition of the two results in an attenuation of labeling, indicating a shift toward outward-facing conformations that can be interpreted using conventional enzyme kinetic analyses. Such measurements can afford the Km for each ligand as well as the stoichiometry of ion-substrate-coupled conformational changes. Mutations that perturb the substrate binding site either result in the protein being unable to adopt outward-facing conformations or in a global destabilization of structure. The methodology combines covalent labeling, mass spectrometry, and kinetic analyses in a straightforward workflow applicable to a range of systems, enabling the interrogation of changes in a protein's conformation required for function at varied concentrations of substrates, and the consequences of mutations on these conformational transitions.
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Affiliation(s)
| | | | | | - Oliver Beckstein
- Department of Physics, Arizona State University , Tempe, Arizona 85287-1504, United States
| | - Florian Heinkel
- Centre for High-Throughput Biology, University of British Columbia , Vancouver, British Columbia, Canada V6T 1Z4
| | - Joerg Gsponer
- Centre for High-Throughput Biology, University of British Columbia , Vancouver, British Columbia, Canada V6T 1Z4
| | | | - Marta Sans
- Hamburg Centre for Ultrafast Imaging, Institute for Nanostructure and Solid State Physics, Universität Hamburg , Hamburg 22761, Germany
| | - Maria Kokkinidou
- Hamburg Centre for Ultrafast Imaging, Institute for Nanostructure and Solid State Physics, Universität Hamburg , Hamburg 22761, Germany
| | - Arwen R Pearson
- Hamburg Centre for Ultrafast Imaging, Institute for Nanostructure and Solid State Physics, Universität Hamburg , Hamburg 22761, Germany
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21
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Lu Y, Zhang H, Niedzwiedzki DM, Jiang J, Blankenship RE, Gross ML. Fast Photochemical Oxidation of Proteins Maps the Topology of Intrinsic Membrane Proteins: Light-Harvesting Complex 2 in a Nanodisc. Anal Chem 2016; 88:8827-34. [PMID: 27500903 PMCID: PMC5201186 DOI: 10.1021/acs.analchem.6b01945] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Although membrane proteins are crucial participants in photosynthesis and other biological processes, many lack high-resolution structures. Prior to achieving a high-resolution structure, we are investigating whether MS-based footprinting can provide coarse-grained protein structure by following structural changes that occur upon ligand binding, pH change, and membrane binding. Our platform probes topology and conformation of membrane proteins by combining MS-based footprinting, specifically fast photochemical oxidation of proteins (FPOP), and lipid Nanodiscs, which are more similar to the native membrane environment than are the widely used detergent micelles. We describe here results that show a protein's outer membrane regions are more heavily footprinted by OH radicals whereas the regions spanning the lipid bilayer remain inert to the labeling. Nanodiscs generally exhibit more protection of membrane proteins compared to detergent micelles and less shielding to those protein residues that exist outside the membrane. The combination of immobilizing the protein in Nanodiscs and footprinting with FPOP is a feasible approach to map extra-membrane protein surfaces, even at the amino-acid level, and to illuminate intrinsic membrane protein topology.
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Affiliation(s)
- Yue Lu
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Hao Zhang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Dariusz M. Niedzwiedzki
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Jing Jiang
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Robert E. Blankenship
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
- Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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22
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Rinas A, Espino JA, Jones LM. An efficient quantitation strategy for hydroxyl radical-mediated protein footprinting using Proteome Discoverer. Anal Bioanal Chem 2016; 408:3021-31. [PMID: 26873216 DOI: 10.1007/s00216-016-9369-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 01/17/2016] [Accepted: 01/27/2016] [Indexed: 01/12/2023]
Abstract
Hydroxyl radical protein footprinting coupled with mass spectrometry has become an invaluable technique for protein structural characterization. In this method, hydroxyl radicals react with solvent exposed amino acid side chains producing stable, covalently attached labels. Although this technique yields beneficial information, the extensive list of known oxidation products produced make the identification and quantitation process considerably complex. Currently, the methods available for analysis either involve manual analysis steps, or limit the amount of searchable modifications or the size of sequence database. This creates a bottleneck which can result in a long and arduous analysis process, which is further compounded in a complex sample. Here, we report the use of a new footprinting analysis method for both peptide and residue-level analysis, demonstrated on the GCaMP2 synthetic construct in calcium free and calcium bound states. This method utilizes a customized multi-search node workflow developed for an on-market search platform in conjunction with a quantitation platform developed using a free Excel add-in. Moreover, the method expedites the analysis process, requiring only two post-search hours to complete quantitation, regardless of the size of the experiment or the sample complexity.
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Affiliation(s)
- Aimee Rinas
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford St LD326, Indianapolis, IN, 46202, USA
| | - Jessica A Espino
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford St LD326, Indianapolis, IN, 46202, USA
| | - Lisa M Jones
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford St LD326, Indianapolis, IN, 46202, USA.
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23
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Cordeiro RM. Molecular dynamics simulations of the transport of reactive oxygen species by mammalian and plant aquaporins. Biochim Biophys Acta Gen Subj 2015; 1850:1786-94. [PMID: 25982446 DOI: 10.1016/j.bbagen.2015.05.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Revised: 05/06/2015] [Accepted: 05/07/2015] [Indexed: 11/25/2022]
Abstract
BACKGROUND Aquaporins are responsible for water transport across lipid membranes. They are also able to transport reactive oxygen species, playing an important role in redox signaling. Certain plant aquaporins have even the ability to be regulated by oxidative stress. However, the underlying mechanisms are still not fully understood. METHODS Here, molecular dynamics simulations were employed to determine the activation free energies related to the transport of reactive oxygen species through both mammalian and plant aquaporin models. RESULTS AND CONCLUSIONS Both aquaporins may transport hydrogen peroxide (H2O2) and the protonated form of superoxide radicals (HO2). The solution-to-pore transfer free energies were low for small oxy-radicals, suggesting that even highly reactive hydroxyl radicals (HO) might have access to the pore interior and oxidize amino acids responsible for channel selectivity. In the plant aquaporin, no significant change in water permeability was observed upon oxidation of the solvent-exposed disulfide bonds at the extracellular region. During the simulated time scale, the existence of a direct oxidative gating mechanism involving these disulfide bonds could not be demonstrated. GENERAL SIGNIFICANCE Simulation results may improve the understanding of redox signaling mechanisms and help in the interpretation of protein oxidative labeling experiments.
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Affiliation(s)
- Rodrigo M Cordeiro
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Avenida dos Estados 5001, CEP 09210-580, Santo André, SP, Brazil.
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24
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Determination of total antioxidant capacity of milk by CUPRAC and ABTS methods with separate characterisation of milk protein fractions. J DAIRY RES 2015; 82:177-84. [DOI: 10.1017/s0022029915000114] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most milk-applied antioxidant assays in literature are based on the isolation and quantification of individual antioxidative compounds, whereas total antioxidant capacity (TAC) gives a more holistic picture due to cooperative action of antioxidants. Recently, the cupric reducing antioxidant capacity (CUPRAC) method has been modified to measure the antioxidant capacities of thiol-containing proteins, where the classical ammonium acetate buffer – that may otherwise precipitate proteins– was replaced with concentrated urea buffer (able to expose embedded thiol groups of proteins to oxidative attack) adjusted to pH 7.0. Thus, antioxidant capacity of milk was investigated with two competing TAC assays, namely CUPRAC and ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid))/persulphate, because only these assays were capable of evaluating protein contribution to the observed TAC value. As milk fat caused turbidity, experiments were carried out with skim milk or defatted milk samples. To determine TAC, modified CUPRAC method was applied to whole milk, separated and redissolved protein fractions, and the remaining liquid phase after necessary operations. Both TAC methods were investigated for their dilution sensitivity and antioxidant power assessment of separate milk fractions such as casein and whey. Proteins like β-lactoglobulin and casein (but not simple thiols) exhibited enhanced CUPRAC reactivity with surfactant (SDS) addition. Addition of milk protein fractions to whole skim milk produced significant ‘negative-biased’ deviations (up to −26% relative standard error) from TAC absorbance additivity in the application of the ABTS method, as opposed to that of the CUPRAC method less affected by chemical deviations from Beer's law thereby producing much smaller deviations from additivity (i.e. the property of additivity is valid when the measured TAC of a mixture is equal to the sum of individual antioxidant capacities of its constituents).
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25
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Yan Y, Chen G, Wei H, Huang RYC, Mo J, Rempel DL, Tymiak AA, Gross ML. Fast photochemical oxidation of proteins (FPOP) maps the epitope of EGFR binding to adnectin. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:2084-92. [PMID: 25267085 PMCID: PMC4224620 DOI: 10.1007/s13361-014-0993-x] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 08/15/2014] [Accepted: 08/21/2014] [Indexed: 05/11/2023]
Abstract
Epitope mapping is an important tool for the development of monoclonal antibodies, mAbs, as therapeutic drugs. Recently, a class of therapeutic mAb alternatives, adnectins, has been developed as targeted biologics. They are derived from the 10th type III domain of human fibronectin ((10)Fn3). A common approach to map the epitope binding of these therapeutic proteins to their binding partners is X-ray crystallography. Although the crystal structure is known for Adnectin 1 binding to human epidermal growth factor receptor (EGFR), we seek to determine complementary binding in solution and to test the efficacy of footprinting for this purpose. As a relatively new tool in structural biology and complementary to X-ray crystallography, protein footprinting coupled with mass spectrometry is promising for protein-protein interaction studies. We report here the use of fast photochemical oxidation of proteins (FPOP) coupled with MS to map the epitope of EGFR-Adnectin 1 at both the peptide and amino-acid residue levels. The data correlate well with the previously determined epitopes from the crystal structure and are consistent with HDX MS data, which are presented in an accompanying paper. The FPOP-determined binding interface involves various amino-acid and peptide regions near the N terminus of EGFR. The outcome adds credibility to oxidative labeling by FPOP for epitope mapping and motivates more applications in the therapeutic protein area as a stand-alone method or in conjunction with X-ray crystallography, NMR, site-directed mutagenesis, and other orthogonal methods.
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Affiliation(s)
- Yuetian Yan
- Center for Biomedical and Bioorganic Mass Spectrometry, Department of Chemistry, Washington University in St. Louis, St. Louis, MO, 63130-4899, USA
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26
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Liuni P, Zhu S, Wilson DJ. Oxidative protein labeling with analysis by mass spectrometry for the study of structure, folding, and dynamics. Antioxid Redox Signal 2014; 21:497-510. [PMID: 24512178 DOI: 10.1089/ars.2014.5850] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
SIGNIFICANCE Analytical approaches that can provide insights into the mechanistic processes underlying protein folding and dynamics are few since the target analytes-high-energy structural intermediates-are short lived and often difficult to distinguish from coexisting structures. Folding "intermediates" can be populated at equilibrium using weakly denaturing solvents, but it is not clear that these species are identical to those that are transiently populated during folding under "native" conditions. Oxidative labeling with mass spectrometric analysis is a powerful alternative for structural characterization of proteins and transient protein species based on solvent exposure at specific sites. RECENT ADVANCES Oxidative labeling is increasingly used with exceedingly short (μs) labeling pulses, both to minimize the occurrence of artifactual structural changes due to the incorporation of label and to detect short-lived species. The recent introduction of facile photolytic approaches for producing reactive oxygen species is an important technological advance that will enable more widespread adoption of the technique. CRITICAL ISSUES The most common critique of oxidative labeling data is that even with brief labeling pulses, covalent modification of the protein may cause significant artifactual structural changes. FUTURE DIRECTIONS While the oxidative labeling with the analysis by mass spectrometry is mature enough that most basic methodological issues have been addressed, a complete systematic understanding of side chain reactivity in the context of intact proteins is an avenue for future work. Specifically, there remain issues around the impact of primary sequence and side chain interactions on the reactivity of "solvent-exposed" residues. Due to its analytical power, wide range of applications, and relative ease of implementation, oxidative labeling is an increasingly important technique in the bioanalytical toolbox.
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Affiliation(s)
- Peter Liuni
- 1 Department of Chemistry, York University , Toronto, Canada
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27
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Lee H, Kim H. Membrane topology of transmembrane proteins: determinants and experimental tools. Biochem Biophys Res Commun 2014; 453:268-76. [PMID: 24938127 DOI: 10.1016/j.bbrc.2014.05.111] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 05/27/2014] [Indexed: 10/25/2022]
Abstract
Membrane topology refers to the two-dimensional structural information of a membrane protein that indicates the number of transmembrane (TM) segments and the orientation of soluble domains relative to the plane of the membrane. Since membrane proteins are co-translationally translocated across and inserted into the membrane, the TM segments orient themselves properly in an early stage of membrane protein biogenesis. Each membrane protein must contain some topogenic signals, but the translocation components and the membrane environment also influence the membrane topology of proteins. We discuss the factors that affect membrane protein orientation and have listed available experimental tools that can be used in determining membrane protein topology.
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Affiliation(s)
- Hunsang Lee
- School of Biological Sciences, Seoul National University, Seoul 151-747, South Korea
| | - Hyun Kim
- School of Biological Sciences, Seoul National University, Seoul 151-747, South Korea.
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28
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High-resolution MS for structural characterization of protein therapeutics: advances and future directions. Bioanalysis 2013; 5:1299-313. [DOI: 10.4155/bio.13.80] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
High-resolution MS (HRMS) is a central analytical technique for the study of biomolecules and is widely used in the biopharmaceutical industry. This paper reviews recent advances in commonly used HRMS instrumentation and experimental strategies for HRMS-based structural characterization of protein therapeutics. An overview of protein higher order structural characterization using HRMS-based technologies is presented, including the use of hydrogen/deuterium exchange and hydroxyl radical footprinting methods for probing protein conformational dynamics and interactions in solution. Future directions in application of HRMS for characterizing protein therapeutics are also described.
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29
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Islam ST, Lam JS. Topological mapping methods for α-helical bacterial membrane proteins--an update and a guide. Microbiologyopen 2013; 2:350-64. [PMID: 23408725 PMCID: PMC3633358 DOI: 10.1002/mbo3.72] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/04/2013] [Accepted: 01/10/2013] [Indexed: 12/19/2022] Open
Abstract
Integral membrane proteins with α-helical transmembrane segments (TMS) are known to play important and diverse roles in prokaryotic cell physiology. The net hydrophobicity of TMS directly corresponds to the observed difficulties in expressing and purifying these proteins, let alone producing sufficient yields for structural studies using two-/three-dimensional (2D/3D) crystallographic or nuclear magnetic resonance methods. To gain insight into the function of these integral membrane proteins, topological mapping has become an important tool to identify exposed and membrane-embedded protein domains. This approach has led to the discovery of protein tracts of functional importance and to the proposition of novel mechanistic hypotheses. In this review, we synthesize the various methods available for topological mapping of α-helical integral membrane proteins to provide investigators with a comprehensive reference for choosing techniques suited to their particular topological queries and available resources.
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Affiliation(s)
- Salim T Islam
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
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30
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Pan Y, Ruan X, Valvano MA, Konermann L. Validation of membrane protein topology models by oxidative labeling and mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:889-898. [PMID: 22410873 DOI: 10.1007/s13361-012-0342-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/12/2012] [Accepted: 01/17/2012] [Indexed: 05/31/2023]
Abstract
Computer-assisted topology predictions are widely used to build low-resolution structural models of integral membrane proteins (IMPs). Experimental validation of these models by traditional methods is labor intensive and requires modifications that might alter the IMP native conformation. This work employs oxidative labeling coupled with mass spectrometry (MS) as a validation tool for computer-generated topology models. ·OH exposure introduces oxidative modifications in solvent-accessible regions, whereas buried segments (e.g., transmembrane helices) are non-oxidizable. The Escherichia coli protein WaaL (O-antigen ligase) is predicted to have 12 transmembrane helices and a large extramembrane domain (Pérez et al., Mol. Microbiol. 2008, 70, 1424). Tryptic digestion and LC-MS/MS were used to map the oxidative labeling behavior of WaaL. Met and Cys exhibit high intrinsic reactivities with ·OH, making them sensitive probes for solvent accessibility assays. Overall, the oxidation pattern of these residues is consistent with the originally proposed WaaL topology. One residue (M151), however, undergoes partial oxidation despite being predicted to reside within a transmembrane helix. Using an improved computer algorithm, a slightly modified topology model was generated that places M151 closer to the membrane interface. On the basis of the labeling data, it is concluded that the refined model more accurately reflects the actual topology of WaaL. We propose that the combination of oxidative labeling and MS represents a useful strategy for assessing the accuracy of IMP topology predictions, supplementing data obtained in traditional biochemical assays. In the future, it might be possible to incorporate oxidative labeling data directly as constraints in topology prediction algorithms.
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Affiliation(s)
- Yan Pan
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
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31
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St-Pierre JF, Bunker A, Róg T, Karttunen M, Mousseau N. Molecular dynamics simulations of the bacterial ABC transporter SAV1866 in the closed form. J Phys Chem B 2012; 116:2934-42. [PMID: 22339391 DOI: 10.1021/jp209126c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ATP binding cassette (ABC) transporter family of proteins contains members involved in ATP-mediated import or export of ligands at the cell membrane. For the case of exporters, the translocation mechanism involves a large-scale conformational change that involves a clothespin-like motion from an inward-facing open state, able to bind ligands and adenosine triphosphate (ATP), to an outward-facing closed state. Our work focuses on SAV1866, a bacterial member of the ABC transporter family for which the structure is known for the closed state. To evaluate the ability of this protein to undergo conformational changes at physiological temperature, we first performed conventional molecular dynamics (MD) on the cocrystallized adenosine diphosphate (ADP)-bound structure and on a nucleotide-free structure. With this assessment of SAV1866's stability, conformational changes were induced by steered molecular dynamics (SMD), in which the nucleotide binding domains (NBD) were pushed apart, simulating the ATP hydrolysis energy expenditure. We found that the transmembrane domain is not easily perturbed by large-scale motions of the NBDs.
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Affiliation(s)
- Jean-François St-Pierre
- Département de Physique and Regroupement Québécois sur les Matériaux de Pointe, Université de Montréal, C.P. 6128, succursale centre-ville, Montréal (Québec), Canada H3C 3J7
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32
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Zhang H, Wen J, Huang RYC, Blankenship RE, Gross ML. Mass spectrometry-based carboxyl footprinting of proteins: method evaluation. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2012; 312:78-86. [PMID: 22408386 PMCID: PMC3293472 DOI: 10.1016/j.ijms.2011.07.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Protein structure determines function in biology, and a variety of approaches have been employed to obtain structural information about proteins. Mass spectrometry-based protein footprinting is one fast-growing approach. One labeling-based footprinting approach is the use of a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and glycine ethyl ester (GEE) to modify solvent-accessible carboxyl groups on glutamate (E) and aspartate (D). This paper describes method development of carboxyl-group modification in protein footprinting. The modification protocol was evaluated by using the protein calmodulin as a model. Because carboxyl-group modification is a slow reaction relative to protein folding and unfolding, there is an issue that modifications at certain sites may induce protein unfolding and lead to additional modification at sites that are not solvent-accessible in the wild-type protein. We investigated this possibility by using hydrogen deuterium amide exchange (H/DX). The study demonstrated that application of carboxyl group modification in probing conformational changes in calmodulin induced by Ca(2+) binding provides useful information that is not compromised by modification-induced protein unfolding.
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Affiliation(s)
- Hao Zhang
- Department of Chemistry, Washington University in St. Louis, MO 63130
| | - Jianzhong Wen
- Department of Chemistry, Washington University in St. Louis, MO 63130
- Department of Biology, Washington University in St. Louis, MO 63130
| | - Richard Y-C Huang
- Department of Chemistry, Washington University in St. Louis, MO 63130
| | - Robert E. Blankenship
- Department of Chemistry, Washington University in St. Louis, MO 63130
- Department of Biology, Washington University in St. Louis, MO 63130
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, MO 63130
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Pacholarz KJ, Garlish RA, Taylor RJ, Barran PE. Mass spectrometry based tools to investigate protein–ligand interactions for drug discovery. Chem Soc Rev 2012; 41:4335-55. [DOI: 10.1039/c2cs35035a] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Pan Y, Brown L, Konermann L. Hydrogen exchange mass spectrometry of bacteriorhodopsin reveals light-induced changes in the structural dynamics of a biomolecular machine. J Am Chem Soc 2011; 133:20237-44. [PMID: 22043856 DOI: 10.1021/ja206197h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Many proteins act as molecular machines that are fuelled by a nonthermal energy source. Examples include transmembrane pumps and stator-rotor complexes. These systems undergo cyclic motions (CMs) that are being driven along a well-defined conformational trajectory. Superimposed on these CMs are thermal fluctuations (TFs) that are coupled to stochastic motions of the solvent. Here we explore whether the TFs of a molecular machine are affected by the occurrence of CMs. Bacteriorhodopsin (BR) is a light-driven proton pump that serves as a model system in this study. The function of BR is based on a photocycle that involves trans/cis isomerization of a retinal chromophore, as well as motions of transmembrane helices. Hydrogen/deuterium exchange (HDX) mass spectrometry was used to monitor the TFs of BR, focusing on the monomeric form of the protein. Comparative HDX studies were conducted under illumination and in the dark. The HDX kinetics of BR are dramatically accelerated in the presence of light. The isotope exchange rates and the number of backbone amides involved in EX2 opening transitions increase roughly 2-fold upon illumination. In contrast, light/dark control experiments on retinal-free protein produced no discernible differences. It can be concluded that the extent of TFs in BR strongly depends on photon-driven CMs. The light-induced differences in HDX behavior are ascribed to protein destabilization. Specifically, the thermodynamic stability of the dark-adapted protein is estimated to be 5.5 kJ mol(-1) under the conditions of our work. This value represents the free energy difference between the folded state F and a significantly unfolded conformer U. Illumination reduces the stability of F by 2.2 kJ mol(-1). Mechanical agitation caused by isomerization of the chromophore is transferred to the surrounding protein scaffold, and subsequently, the energy dissipates into the solvent. Light-induced retinal motions therefore act analogously to an internal heat source that promotes the occurrence of TFs. Overall, our data highlight the potential of HDX methods for probing the structural dynamics of molecular machines under "engine on" and "engine off" conditions.
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Affiliation(s)
- Yan Pan
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
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35
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Jones LM, B Sperry J, A Carroll J, Gross ML. Fast photochemical oxidation of proteins for epitope mapping. Anal Chem 2011; 83:7657-61. [PMID: 21894996 PMCID: PMC3193551 DOI: 10.1021/ac2007366] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The growing use of monoclonal antibodies as therapeutics underscores the importance of epitope mapping as an essential step in characterizing antibody-antigen complexes. The use of protein footprinting coupled with mass spectrometry, which is emerging as a tool in structural biology, offers opportunities to map antibody-binding regions of antigens. We report here the use of footprinting via fast photochemical oxidation of proteins (FPOP) with OH radicals to characterize the epitope of the serine protease thrombin. The data correlate well with previously published results that determined the epitope of thrombin. This study marks the first time oxidative labeling has been used for epitope mapping.
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Affiliation(s)
- Lisa M Jones
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA.
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36
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Barrera NP, Robinson CV. Advances in the mass spectrometry of membrane proteins: from individual proteins to intact complexes. Annu Rev Biochem 2011; 80:247-71. [PMID: 21548785 DOI: 10.1146/annurev-biochem-062309-093307] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Rapid advances in structural genomics and in large-scale proteomic projects have yielded vast amounts of data on soluble proteins and their complexes. Despite these advances, progress in studying membrane proteins using mass spectrometry (MS) has been slow. This is due in part to the inherent solubility and dynamic properties of these proteins, but also to their low abundance and the absence of polar side chains in amino acid residues. Considerable progress in overcoming these challenges is, however, now being made for all levels of structural characterization. This progress includes MS studies of the primary structure of membrane proteins, wherein sophisticated enrichment and trapping procedures are allowing multiple posttranslational modifications to be defined through to the secondary structure level in which proteins and peptides have been probed using hydrogen exchange, covalent, or radiolytic labeling methods. Exciting possibilities now exist to go beyond primary and secondary structure to reveal the tertiary and quaternary interactions of soluble and membrane subunits within intact assemblies of more than 700 kDa.
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Affiliation(s)
- Nelson P Barrera
- Department of Physiology, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile.
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37
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Mass spectrometry accelerates membrane protein analysis. Trends Biochem Sci 2011; 36:388-96. [PMID: 21616670 DOI: 10.1016/j.tibs.2011.04.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 04/19/2011] [Accepted: 04/19/2011] [Indexed: 12/25/2022]
Abstract
Cellular membranes are composed of proteins and glyco- and phospholipids and play an indispensible role in maintaining cellular integrity and homeostasis, by physically restricting biochemical processes within cells and providing protection. Membrane proteins perform many essential functions, which include operating as transporters, adhesion-anchors, receptors, and enzymes. Recent advancements in proteomic mass spectrometry have resulted in substantial progress towards the determination of the plasma membrane (PM) proteome, resolution of membrane protein topology, establishment of numerous receptor protein complexes, identification of ligand-receptor pairs, and the elucidation of signaling networks originating at the PM. Here, we discuss the recent accelerated success of discovery-based proteomic pipelines for the establishment of a complete membrane proteome.
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Kinetic folding mechanism of an integral membrane protein examined by pulsed oxidative labeling and mass spectrometry. J Mol Biol 2011; 410:146-58. [PMID: 21570983 DOI: 10.1016/j.jmb.2011.04.074] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 04/26/2011] [Accepted: 04/29/2011] [Indexed: 11/21/2022]
Abstract
We report the application of pulsed oxidative labeling for deciphering the folding mechanism of a membrane protein. SDS-denatured bacteriorhodopsin (BR) was refolded by mixing with bicelles in the presence of free retinal. At various time points (20 ms to 1 day), the protein was exposed to a microsecond ·OH pulse that induces oxidative modifications at solvent-accessible methionine side chains. The extent of labeling was determined by mass spectrometry. These measurements were complemented by stopped-flow spectroscopy. Major time-dependent changes in solvent accessibility were detected for M20 (helix A) and M118 (helix D). Our kinetic data indicate a sequential folding mechanism, consistent with models previously suggested by others on the basis of optical data. Yet, ·OH labeling provides additional structural insights. An initial folding intermediate I(1) gets populated within 20 ms, concomitantly with formation of helix A. Subsequent structural consolidation leads to a transient species I(2). Noncovalent retinal binding to I(2) induces folding of helix D, thereby generating an intermediate I(R). In the absence of retinal, the latter transition does not take place. Hence, formation of helix D depends on retinal binding, whereas this is not the case for helix A. As the cofactor settles deeper into its binding pocket, a final transient species I(R) is generated. This intermediate converts into native BR within minutes by formation of the retinal-K216 Schiff base linkage. The combination of pulsed covalent labeling and optical spectroscopy employed here should also be suitable for exploring the folding mechanisms of other membrane proteins.
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Zhang H, Shen W, Rempel D, Monsey J, Vidavsky I, Gross ML, Bose R. Carboxyl-group footprinting maps the dimerization interface and phosphorylation-induced conformational changes of a membrane-associated tyrosine kinase. Mol Cell Proteomics 2011; 10:M110.005678. [PMID: 21422241 DOI: 10.1074/mcp.m110.005678] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Her4 is a transmembrane receptor tyrosine kinase belonging to the ErbB-EGFR family. It plays a vital role in the cardiovascular and nervous systems, and mutations in Her4 have been found in melanoma and lung cancer. The kinase domain of Her4 forms a dimer complex, called the asymmetric dimer, which results in kinase activation. Although a crystal structure of the Her4 asymmetric dimer is known, the dimer affinity and the effect of the subsequent phosphorylation steps on kinase domain conformation are unknown. We report here the use of carboxyl-group footprinting MS on a recombinant expressed, Her4 kinase-domain construct to address these questions. Carboxyl-group footprinting uses a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, in the presence of glycine ethyl ester, to modify accessible carboxyl groups on glutamate and aspartate residues. Comparisons of Her4 kinase-domain monomers versus dimers and of unphosphorylated versus phosphorylated dimers were made to map the dimerization interface and to determine phosphorylation induced-conformational changes. We detected 37 glutamate and aspartate residues that were modified, and we quantified their extents of modification by liquid chromatography MS. Five residues showed changes in carboxyl-group modification. Three of these residues are at the predicted dimer interface, as shown by the crystal structure, and the remaining two residues are on loops that likely have altered conformation in the kinase dimer. Incubating the Her4 kinase dimers with ATP resulted in dramatic increase in Tyr-850 phosphorylation, located on the activation loop, and this resulted in a conformational change in this loop, as evidenced by reduction in carboxyl-group modification. The kinase monomer-dimer equilibrium was measured using a titration format in which the extent of carboxyl-group footprinting was mathematically modeled to give the dimer association constant (1.5-6.8 × 10(12) dm(2)/mol). This suggests that the kinase-domain makes a significant contribution to the overall dimerization affinity of the full-length Her4 protein.
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Affiliation(s)
- Hao Zhang
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
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40
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Pan Y, Brown L, Konermann L. Site-directed mutagenesis combined with oxidative methionine labeling for probing structural transitions of a membrane protein by mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1947-1956. [PMID: 20829064 DOI: 10.1016/j.jasms.2010.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 08/06/2010] [Accepted: 08/09/2010] [Indexed: 05/29/2023]
Abstract
Exposure of the membrane protein bacteriorhodopsin (BR) to SDS induces partial breakdown of the native conformation. The exact structural properties of this SDS state remain a matter of debate, despite its widespread use in BR folding experiments. The current work employs hydroxyl radical (·OH) labeling in conjunction with mass spectrometry (MS)-based peptide mapping for probing the solvent accessibility of individual BR segments in the presence of SDS. Previous work revealed methionine sulfoxide formation to be the dominant oxidative pathway. Those data suggested extensive unfolding of helices A and D in SDS. Unfortunately, the lack of Met residues in helices C and F implies that no direct information on the behavior of the latter two elements could be obtained. Here, we address this problem by employing two variants with additional Met residues, L93M (helix C) and V179M (helix F). The oxidation behavior of the resulting 11 methionines can be grouped into three categories: (1) extensively labeled both in native BR and in SDS (loop residues M32, M68, and M163); (2) protected in the native state but not in SDS (M20, M118); (3) always protected (M56, M60, M93, M145, M179, M209). These data show that a solvent-inaccessible core is retained in SDS. This core consists of partially intact helices B, C, E, F, and G. The termini of these helices are highly dynamic and/or unraveled, particularly on the cytoplasmic side. Overall, this work demonstrates how the use of engineered ·OH labeling sites can provide insights into structural properties of membrane proteins.
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Affiliation(s)
- Yan Pan
- Department of Chemistry, University of Western Ontario, London, Ontario, Canada
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41
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Roeser J, Bischoff R, Bruins AP, Permentier HP. Oxidative protein labeling in mass-spectrometry-based proteomics. Anal Bioanal Chem 2010; 397:3441-55. [PMID: 20155254 PMCID: PMC2911539 DOI: 10.1007/s00216-010-3471-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 01/07/2023]
Abstract
Oxidation of proteins and peptides is a common phenomenon, and can be employed as a labeling technique for mass-spectrometry-based proteomics. Nonspecific oxidative labeling methods can modify almost any amino acid residue in a protein or only surface-exposed regions. Specific agents may label reactive functional groups in amino acids, primarily cysteine, methionine, tyrosine, and tryptophan. Nonspecific radical intermediates (reactive oxygen, nitrogen, or halogen species) can be produced by chemical, photochemical, electrochemical, or enzymatic methods. More targeted oxidation can be achieved by chemical reagents but also by direct electrochemical oxidation, which opens the way to instrumental labeling methods. Oxidative labeling of amino acids in the context of liquid chromatography(LC)-mass spectrometry (MS) based proteomics allows for differential LC separation, improved MS ionization, and label-specific fragmentation and detection. Oxidation of proteins can create new reactive groups which are useful for secondary, more conventional derivatization reactions with, e.g., fluorescent labels. This review summarizes reactions of oxidizing agents with peptides and proteins, the corresponding methodologies and instrumentation, and the major, innovative applications of oxidative protein labeling described in selected literature from the last decade.
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Affiliation(s)
- Julien Roeser
- Analytical Biochemistry and Mass Spectrometry Core Facility, Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Rainer Bischoff
- Analytical Biochemistry and Mass Spectrometry Core Facility, Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Andries P. Bruins
- Analytical Biochemistry and Mass Spectrometry Core Facility, Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Hjalmar P. Permentier
- Analytical Biochemistry and Mass Spectrometry Core Facility, Department of Pharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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42
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Konermann L, Stocks BB, Pan Y, Tong X. Mass spectrometry combined with oxidative labeling for exploring protein structure and folding. MASS SPECTROMETRY REVIEWS 2010; 29:651-667. [PMID: 19672951 DOI: 10.1002/mas.20256] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This review discusses various mass spectrometry (MS)-based approaches for exploring structural aspects of proteins in solution. Electrospray ionization (ESI)-MS, in particular, has found fascinating applications in this area. For example, when used in conjunction with solution-phase hydrogen/deuterium exchange (HDX), ESI-MS is a highly sensitive tool for probing conformational dynamics. The main focus of this article is a technique that is complementary to HDX, that is, the covalent labeling of proteins by hydroxyl radicals. The reactivity of individual amino acid side chains with *OH is strongly affected by their degree of solvent exposure. Thus, analysis of the oxidative labeling pattern by peptide mapping and tandem mass spectrometry provides detailed structural information. A convenient method for *OH production is the photolysis of H(2)O(2) by a pulsed UV laser, resulting in oxidative labeling on the microsecond time scale. Selected examples demonstrate the use of this technique for structural studies on membrane proteins, and the combination with rapid mixing devices for characterizing the properties of short-lived protein (un)folding intermediates.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
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43
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Trimpin S. A perspective on MALDI alternatives-total solvent-free analysis and electron transfer dissociation of highly charged ions by laserspray ionization. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:471-485. [PMID: 20446310 DOI: 10.1002/jms.1737] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Progress in research is hindered by analytical limitations, especially in biological areas in which sensitivity and dynamic range are critical to success. Inherent difficulties of characterization associated with complexity arising from heterogeneity of various materials including topologies (isomeric composition) and insolubility also limit progress. For this reason, we are developing methods for total solvent-free analysis by mass spectrometry consisting of solvent-free ionization followed by solvent-free gas-phase separation. We also recently constructed a novel matrix-assisted laser desorption ionization (MALDI) source that provides a simple, practical and sensitive way of producing highly charged ions by laserspray ionization (LSI) or singly charged ions commonly observed with MALDI by choice of matrix or matrix preparation. This is the first ionization source with such freedom-an extremely powerful analytical 'switch'. Multiply charged LSI ions allow molecules exceeding the mass-to-charge range of the instrument to be observed and permit for the first time electron transfer dissociation fragment ion analysis.
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Affiliation(s)
- Sarah Trimpin
- Department of Chemistry, Wayne State University, Detroit, MI, USA.
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44
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Xia Y, Cooks RG. Plasma Induced Oxidative Cleavage of Disulfide Bonds in Polypeptides during Nanoelectrospray Ionization. Anal Chem 2010; 82:2856-64. [PMID: 20196567 DOI: 10.1021/ac9028328] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yu Xia
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
| | - R. Graham Cooks
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393
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45
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Pan Y, Konermann L. Membrane protein structural insights from chemical labeling and mass spectrometry. Analyst 2010; 135:1191-200. [DOI: 10.1039/b924805f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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46
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Pan Y, Brown L, Konermann L. Mapping the Structure of an Integral Membrane Protein under Semi-Denaturing Conditions by Laser-Induced Oxidative Labeling and Mass Spectrometry. J Mol Biol 2009; 394:968-81. [DOI: 10.1016/j.jmb.2009.09.063] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Revised: 09/28/2009] [Accepted: 09/28/2009] [Indexed: 12/23/2022]
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47
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Abstract
The analysis of insoluble proteins represents a major technical challenge for the field of proteomics. For example, membrane proteins are often insoluble in common solvents and represent 20-30% of the proteins encoded by the human genome. Chemical analysis on an individual basis is often required and is laborious and time consuming. This review presents an overview of methods for purification of expressed proteins using fusion tags as well as methods for analysis of insoluble proteins by mass spectrometry with a goal of achieving high-throughput analysis.
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Affiliation(s)
- Sarah Trimpin
- Department of Chemistry, Wayne State University, Department of Chemistry, Detroit, Michigan, USA
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48
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Abstract
The analysis of insoluble proteins represents a major technical challenge for the field of proteomics. For example, membrane proteins are often insoluble in common solvents and represent 20–30% of the proteins encoded by the human genome. Chemical analysis on an individual basis is often required and is laborious and time-consuming. This review presents an overview of methods for purification of expressed proteins using fusion tags as well as methods for analysis of insoluble proteins by mass spectrometry with a goal of achieving high-throughput analysis.
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49
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Boys BL, Kuprowski MC, Noël JJ, Konermann L. Protein Oxidative Modifications During Electrospray Ionization: Solution Phase Electrochemistry or Corona Discharge-Induced Radical Attack? Anal Chem 2009; 81:4027-34. [DOI: 10.1021/ac900243p] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Brian L. Boys
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Mark C. Kuprowski
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - James J. Noël
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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