1
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Khaje NA, Eletsky A, Biehn SE, Mobley CK, Rogals MJ, Kim Y, Mishra SK, Doerksen RJ, Lindert S, Prestegard JH, Sharp JS. Validated determination of NRG1 Ig-like domain structure by mass spectrometry coupled with computational modeling. Commun Biol 2022; 5:452. [PMID: 35551273 PMCID: PMC9098640 DOI: 10.1038/s42003-022-03411-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 04/25/2022] [Indexed: 01/03/2023] Open
Abstract
High resolution hydroxyl radical protein footprinting (HR-HRPF) is a mass spectrometry-based method that measures the solvent exposure of multiple amino acids in a single experiment, offering constraints for experimentally informed computational modeling. HR-HRPF-based modeling has previously been used to accurately model the structure of proteins of known structure, but the technique has never been used to determine the structure of a protein of unknown structure. Here, we present the use of HR-HRPF-based modeling to determine the structure of the Ig-like domain of NRG1, a protein with no close homolog of known structure. Independent determination of the protein structure by both HR-HRPF-based modeling and heteronuclear NMR was carried out, with results compared only after both processes were complete. The HR-HRPF-based model was highly similar to the lowest energy NMR model, with a backbone RMSD of 1.6 Å. To our knowledge, this is the first use of HR-HRPF-based modeling to determine a previously uncharacterized protein structure. A mass spectrometry-based method guides computational modeling for de novo protein structure prediction.
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Affiliation(s)
- Niloofar Abolhasani Khaje
- Department of BioMolecular Sciences, University of Mississippi, University, MS, USA.,Analytical Operations Department, Gilead Sciences, Foster City, CA, USA
| | - Alexander Eletsky
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Sarah E Biehn
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - Charles K Mobley
- Department of BioMolecular Sciences, University of Mississippi, University, MS, USA.,Protein Discovery Department, Impossible Foods, Redwood City, CA, USA
| | - Monique J Rogals
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Yoonkyoo Kim
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Sushil K Mishra
- Department of BioMolecular Sciences, University of Mississippi, University, MS, USA.,Glycoscience Center of Research Excellence, University of Mississippi, University, MS, USA
| | - Robert J Doerksen
- Department of BioMolecular Sciences, University of Mississippi, University, MS, USA.,Glycoscience Center of Research Excellence, University of Mississippi, University, MS, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH, USA
| | - James H Prestegard
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, USA
| | - Joshua S Sharp
- Department of BioMolecular Sciences, University of Mississippi, University, MS, USA. .,Glycoscience Center of Research Excellence, University of Mississippi, University, MS, USA. .,Department of Chemistry and Biochemistry, University of Mississippi, University, MS, USA.
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2
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Sharp JS, Chea EE, Misra SK, Orlando R, Popov M, Egan RW, Holman D, Weinberger SR. Flash Oxidation (FOX) System: A Novel Laser-Free Fast Photochemical Oxidation Protein Footprinting Platform. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1601-1609. [PMID: 33872496 PMCID: PMC8812269 DOI: 10.1021/jasms.0c00471] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Hydroxyl radical protein footprinting (HRPF) is a powerful and flexible technique for probing changes in protein topography. With the development of the fast photochemical oxidation of proteins (FPOP), it became possible for researchers to perform HRPF in their laboratory on a very short time scale. While FPOP has grown significantly in popularity since its inception, adoption remains limited due to technical and safety issues involved in the operation of a hazardous Class IV UV laser and irreproducibility often caused by improper laser operation and/or differential radical scavenging by various sample components. Here, we present a new integrated FOX (Flash OXidation) Protein Footprinting System. This platform delivers sample via flow injection to a facile and safe-to-use high-pressure flash lamp with a flash duration of 10 μs fwhm. Integrated optics collect the radiant light and focus it into the lumen of a capillary flow cell. An inline radical dosimeter measures the hydroxyl radical dose delivered and allows for real-time compensation for differential radical scavenging. A programmable fraction collector collects and quenches only the sample that received the desired effective hydroxyl radical dose, diverting the carrier liquid and improperly oxidized sample to waste. We demonstrate the utility of the FOX Protein Footprinting System by determining the epitope of TNFα recognized by adalimumab. We successfully identify the surface of the protein that serves as the epitope for adalimumab, identifying four of the five regions previously noted by X-ray crystallography while seeing no changes in peptides not involved in the epitope interface. The FOX Protein Footprinting System allows for FPOP-like experiments with real-time dosimetry in a safe, compact, and integrated benchtop platform.
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Affiliation(s)
- Joshua S. Sharp
- GenNext Technologies, Inc., Half Moon Bay, CA 94019
- Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, University, Mississippi 38677
- Department of Chemistry and Biochemistry, University of Mississippi, University, Mississippi 38677
- Correspondence to Joshua S. Sharp,
| | | | - Sandeep K. Misra
- Department of BioMolecular Sciences, School of Pharmacy, University of Mississippi, University, Mississippi 38677
| | - Ron Orlando
- GenNext Technologies, Inc., Half Moon Bay, CA 94019
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602
- GlycoScientific, Athens, GA 30602
| | | | | | - David Holman
- GenNext Technologies, Inc., Half Moon Bay, CA 94019
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3
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Kiselar J, Chance MR. High-Resolution Hydroxyl Radical Protein Footprinting: Biophysics Tool for Drug Discovery. Annu Rev Biophys 2018. [DOI: 10.1146/annurev-biophys-070317-033123] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Hydroxyl radical footprinting (HRF) of proteins with mass spectrometry (MS) is a widespread approach for assessing protein structure. Hydroxyl radicals react with a wide variety of protein side chains, and the ease with which radicals can be generated (by radiolysis or photolysis) has made the approach popular with many laboratories. As some side chains are less reactive and thus cannot be probed, additional specific and nonspecific labeling reagents have been introduced to extend the approach. At the same time, advances in liquid chromatography and MS approaches permit an examination of the labeling of individual residues, transforming the approach to high resolution. Lastly, advances in understanding of the chemistry of the approach have led to the determination of absolute protein topologies from HRF data. Overall, the technology can provide precise and accurate measures of side-chain solvent accessibility in a wide range of interesting and useful contexts for the study of protein structure and dynamics in both academia and industry.
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Affiliation(s)
- Janna Kiselar
- Center for Proteomics and Bioinformatics, and Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Mark R. Chance
- Center for Proteomics and Bioinformatics, and Department of Nutrition, Case Western Reserve University, Cleveland, Ohio 44106, USA
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4
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Vandermarliere E, Stes E, Gevaert K, Martens L. Resolution of protein structure by mass spectrometry. MASS SPECTROMETRY REVIEWS 2016; 35:653-665. [PMID: 25536908 DOI: 10.1002/mas.21450] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 10/14/2014] [Indexed: 06/04/2023]
Abstract
Typically, mass spectrometry is used to identify the peptides present in a complex peptide mixture and subsequently the precursor proteins. As such, mass spectrometry focuses mainly on the primary structure, the (modified) amino acid sequence of peptides and proteins. In contrast, the three-dimensional structure of a protein is typically determined with protein X-ray crystallography or NMR. Despite the close relationship between these two aspects of protein studies (sequence and structure), mass spectrometry and structure determination are not frequently combined. Nevertheless, this combination of approaches, dubbed conformational proteomics, can offer insight into the function, working mechanism, and conformational status of a protein. In this review, we will discuss the developments at the intersection of mass spectrometry-based proteomics and protein structure determination and start from a brief overview of the classic approaches to identify protein structure along with their advantages and disadvantages. We will subsequently discuss the ability of mass spectrometry to overcome some of the hurdles of these classic methods. Finally, we will provide an outlook on the interplay of mass spectrometry and protein structure determination, and highlight several recent experiments in which mass spectrometry was successfully used to either aid or complement structure elucidation. © 2014 Wiley Periodicals, Inc. Mass Spec Rev 35:653-665, 2016.
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Affiliation(s)
- Elien Vandermarliere
- Department of Medical Protein Research, VIB, B-9000, Ghent, Belgium
- Department of Biochemistry, Ghent University, B- 9000, Ghent, Belgium
| | - Elisabeth Stes
- Department of Medical Protein Research, VIB, B-9000, Ghent, Belgium
- Department of Biochemistry, Ghent University, B- 9000, Ghent, Belgium
| | - Kris Gevaert
- Department of Medical Protein Research, VIB, B-9000, Ghent, Belgium
- Department of Biochemistry, Ghent University, B- 9000, Ghent, Belgium
| | - Lennart Martens
- Department of Medical Protein Research, VIB, B-9000, Ghent, Belgium.
- Department of Biochemistry, Ghent University, B- 9000, Ghent, Belgium.
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5
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Misko TA, Wijerathna SR, Radivoyevitch T, Berdis AJ, Ahmad MF, Harris ME, Dealwis CG. Inhibition of yeast ribonucleotide reductase by Sml1 depends on the allosteric state of the enzyme. FEBS Lett 2016; 590:1704-12. [PMID: 27155231 DOI: 10.1002/1873-3468.12207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/19/2016] [Accepted: 04/29/2016] [Indexed: 11/05/2022]
Abstract
Sml1 is an intrinsically disordered protein inhibitor of Saccharomyces cerevisiae ribonucleotide reductase (ScRR1), but its inhibition mechanism is poorly understood. RR reduces ribonucleoside diphosphates to their deoxy forms, and balances the nucleotide pool. Multiple turnover kinetics show that Sml1 inhibition of dGTP/ADP- and ATP/CDP-bound ScRR follows a mixed inhibition mechanism. However, Sml1 cooperatively binds to the ES complex in the dGTP/ADP form, whereas with ATP/CDP, Sml1 binds weakly and noncooperatively. Gel filtration and mutagenesis studies indicate that Sml1 does not alter the oligomerization equilibrium and the CXXC motif is not involved in the inhibition. The data suggest that Sml1 is an allosteric inhibitor.
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Affiliation(s)
- Tessianna A Misko
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Sanath R Wijerathna
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Tomas Radivoyevitch
- Department of Quantitative Health Sciences, Cleveland Clinic Foundation, OH, USA
| | | | - Md Faiz Ahmad
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
| | - Michael E Harris
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH, USA
| | - Chris G Dealwis
- Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA
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6
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Xie B, Sharp JS. Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method. Anal Chem 2015; 87:10719-23. [PMID: 26455423 DOI: 10.1021/acs.analchem.5b02865] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydroxyl radical protein footprinting (HRPF) by fast photochemical oxidation of proteins (FPOP) is a powerful benchtop tool used to probe protein structure, interactions, and conformational changes in solution. However, the reproducibility of all HRPF techniques is limited by the ability to deliver a defined concentration of hydroxyl radicals to the protein. This ability is impacted by both the amount of radical generated and the presence of radical scavengers in solution. In order to compare HRPF data from sample to sample, a hydroxyl radical dosimeter is needed that can measure the effective concentration of radical that is delivered to the protein, after accounting for both differences in hydroxyl radical generation and nonanalyte radical consumption. Here, we test three radical dosimeters (Alexa Fluor 488, terepthalic acid, and adenine) for their ability to quantitatively measure the effective radical dose under the high radical concentration conditions of FPOP. Adenine has a quantitative relationship between UV spectrophotometric response, effective hydroxyl radical dose delivered, and peptide and protein oxidation levels over the range of radical concentrations typically encountered in FPOP. The simplicity of an adenine-based dosimeter allows for convenient and flexible incorporation into FPOP applications, and the ability to accurately measure the delivered radical dose will enable reproducible and reliable FPOP across a variety of platforms and applications.
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Affiliation(s)
- Boer Xie
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
| | - Joshua S Sharp
- Complex Carbohydrate Research Center, University of Georgia , Athens, Georgia 30602, United States
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7
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Pilau EJ, Iglesias AH, Gozzo FC. A new label-free approach for the determination of reaction rates in oxidative footprinting experiments. Anal Bioanal Chem 2013; 405:7679-86. [DOI: 10.1007/s00216-013-7247-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 07/08/2013] [Accepted: 07/10/2013] [Indexed: 11/29/2022]
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8
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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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9
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Running WE, Ni P, Kao CC, Reilly JP. Chemical reactivity of brome mosaic virus capsid protein. J Mol Biol 2012; 423:79-95. [PMID: 22750573 DOI: 10.1016/j.jmb.2012.06.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 12/12/2022]
Abstract
Viral particles are biological machines that have evolved to package, protect, and deliver the viral genome into the host via regulated conformational changes of virions. We have developed a procedure to modify lysine residues with S-methylthioacetimidate across the pH range from 5.5 to 8.5. Lysine residues that are not completely modified are involved in tertiary or quaternary structural interactions, and their extent of modification can be quantified as a function of pH. This procedure was applied to the pH-dependent structural transitions of brome mosaic virus (BMV). As the reaction pH increases from 5.5 to 8.5, the average number of modified lysine residues in the BMV capsid protein increases from 6 to 12, correlating well with the known pH-dependent swelling behavior of BMV virions. The extent of reaction of each of the capsid protein's lysine residues has been quantified at eight pH values using coupled liquid chromatography-tandem mass spectrometry. Each lysine can be assigned to one of three structural classes identified by inspection of the BMV virion crystal structure. Several lysine residues display reactivity that indicates their involvement in dynamic interactions that are not obvious in the crystal structure. The influence of several capsid protein mutants on the pH-dependent structural transition of BMV has also been investigated. Mutant H75Q exhibits an altered swelling transition accompanying solution pH increases. The H75Q capsids show increased reactivity at lysine residues 64 and 130, residues distal from the dimer interface occupied by H75, across the entire pH range.
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Affiliation(s)
- W E Running
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
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10
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Myosin binding surface on actin probed by hydroxyl radical footprinting and site-directed labels. J Mol Biol 2011; 414:204-16. [PMID: 21986200 DOI: 10.1016/j.jmb.2011.09.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 09/09/2011] [Accepted: 09/20/2011] [Indexed: 11/22/2022]
Abstract
Actin and myosin are the two main proteins required for cell motility and muscle contraction. The structure of their strongly bound complex-rigor state-is a key for delineating the functional mechanism of actomyosin motor. Current knowledge of that complex is based on models obtained from the docking of known atomic structures of actin and myosin subfragment 1 (S1; the head and neck region of myosin) into low-resolution electron microscopy electron density maps, which precludes atomic- or side-chain-level information. Here, we use radiolytic protein footprinting for global mapping of sites across the actin molecules that are impacted directly or allosterically by myosin binding to actin filaments. Fluorescence and electron paramagnetic resonance spectroscopies and cysteine actin mutants are used for independent, residue-specific probing of S1 effects on two structural elements of actin. We identify actin residue candidates involved in S1 binding and provide experimental evidence to discriminate between the regions of hydrophobic and electrostatic interactions. Focusing on the role of the DNase I binding loop (D-loop) and the W-loop residues of actin in their interactions with S1, we found that the emission properties of acrylodan and the mobility of electron paramagnetic resonance spin labels attached to cysteine mutants of these residues change strongly and in a residue-specific manner upon S1 binding, consistent with the recently proposed direct contacts of these loops with S1. As documented in this study, the direct and indirect changes on actin induced by myosin are more extensive than known until now and attest to the importance of actin dynamics to actomyosin function.
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11
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Schorzman AN, Perera L, Cutalo-Patterson JM, Pedersen LC, Pedersen LG, Kunkel TA, Tomer KB. Modeling of the DNA-binding site of yeast Pms1 by mass spectrometry. DNA Repair (Amst) 2011; 10:454-65. [PMID: 21354867 PMCID: PMC3084373 DOI: 10.1016/j.dnarep.2011.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 01/07/2011] [Accepted: 01/24/2011] [Indexed: 11/26/2022]
Abstract
Mismatch repair (MMR) corrects replication errors that would otherwise lead to mutations and, potentially, various forms of cancer. Among several proteins required for eukaryotic MMR, MutLα is a heterodimer comprised of Mlh1 and Pms1. The two proteins dimerize along their C-terminal domains (CTDs), and the CTD of Pms1 houses a latent endonuclease that is required for MMR. The highly conserved N-terminal domains (NTDs) independently bind DNA and possess ATPase active sites. Here we use two protein footprinting techniques, limited proteolysis and oxidative surface mapping, coupled with mass spectrometry to identify amino acids involved along the DNA-binding surface of the Pms1-NTD. Limited proteolysis experiments elucidated several basic residues that were protected in the presence of DNA, while oxidative surface mapping revealed one residue that is uniquely protected from oxidation. Furthermore, additional amino acids distributed throughout the Pms1-NTD were protected from oxidation either in the presence of a non-hydrolyzable analog of ATP or DNA, indicating that each ligand stabilizes the protein in a similar conformation. Based on the recently published X-ray crystal structure of yeast Pms1-NTD, a model of the Pms1-NTD/DNA complex was generated using the mass spectrometric data as constraints. The proposed model defines the DNA-binding interface along a positively charged groove of the Pms1-NTD and complements prior mutagenesis studies of Escherichia coli and eukaryotic MutL.
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Affiliation(s)
- Allison N. Schorzman
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lalith Perera
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Jenny M. Cutalo-Patterson
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lars C. Pedersen
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lee G. Pedersen
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Thomas A. Kunkel
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Kenneth B. Tomer
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
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12
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Kiselar JG, Chance MR. Future directions of structural mass spectrometry using hydroxyl radical footprinting. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:1373-82. [PMID: 20812376 PMCID: PMC3012749 DOI: 10.1002/jms.1808] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposure of proteins to a 'white' X-ray beam for milliseconds provides sufficient oxidative modification to surface amino acid side chains, which can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular subdomains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review, we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that the selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal-to-noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis-driven structural mass spectrometry experiments.
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Affiliation(s)
- Janna G Kiselar
- Center for Proteomics and Bioinformatics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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13
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Fabris D, Yu ET. Elucidating the higher-order structure of biopolymers by structural probing and mass spectrometry: MS3D. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:841-60. [PMID: 20648672 PMCID: PMC3432860 DOI: 10.1002/jms.1762] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Chemical probing represents a very versatile alternative for studying the structure and dynamics of substrates that are intractable by established high-resolution techniques. The implementation of MS-based strategies for the characterization of probing products has not only extended the range of applicability to virtually all types of biopolymers but has also paved the way for the introduction of new reagents that would not have been viable with traditional analytical platforms. As the availability of probing data is steadily increasing on the wings of the development of dedicated interpretation aids, powerful computational approaches have been explored to enable the effective utilization of such information to generate valid molecular models. This combination of factors has contributed to making the possibility of obtaining actual 3D structures by MS-based technologies (MS3D) a reality. Although approaches for achieving structure determination of unknown targets or assessing the dynamics of known structures may share similar reagents and development trajectories, they clearly involve distinctive experimental strategies, analytical concerns and interpretation paradigms. This Perspective offers a commentary on methods aimed at obtaining distance constraints for the modeling of full-fledged structures while highlighting common elements, salient distinctions and complementary capabilities exhibited by methods used in dynamics studies. We discuss critical factors to be addressed for completing effective structural determinations and expose possible pitfalls of chemical methods. We survey programs developed for facilitating the interpretation of experimental data and discuss possible computational strategies for translating sparse spatial constraints into all-atom models. Examples are provided to illustrate how the concerted application of very diverse probing techniques can lead to the solution of actual biological systems.
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Affiliation(s)
- Daniele Fabris
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD, USA.
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14
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Orban T, Gupta S, Palczewski K, Chance MR. Visualizing water molecules in transmembrane proteins using radiolytic labeling methods. Biochemistry 2010; 49:827-34. [PMID: 20047303 DOI: 10.1021/bi901889t] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Essential to cells and their organelles, water is both shuttled to where it is needed and trapped within cellular compartments and structures. Moreover, ordered waters within protein structures often colocalize with strategically placed polar or charged groups critical for protein function, yet it is unclear if these ordered water molecules provide structural stabilization, mediate conformational changes in signaling, neutralize charged residues, or carry out a combination of all these functions. Structures of many integral membrane proteins, including G protein-coupled receptors (GPCRs), reveal the presence of ordered water molecules that may act like prosthetic groups in a manner quite unlike bulk water. Identification of "ordered" waters within a crystalline protein structure requires sufficient occupancy of water to enable its detection in the protein's X-ray diffraction pattern, and thus, the observed waters likely represent a subset of tightly bound functional waters. In this review, we highlight recent studies that suggest the structures of ordered waters within GPCRs are as conserved (and thus as important) as conserved side chains. In addition, methods of radiolysis, coupled to structural mass spectrometry (protein footprinting), reveal dynamic changes in water structure that mediate transmembrane signaling. The idea of water as a prosthetic group mediating chemical reaction dynamics is not new in fields such as catalysis. However, the concept of water as a mediator of conformational dynamics in signaling is just emerging, because of advances in both crystallographic structure determination and new methods of protein footprinting. Although oil and water do not mix, understanding the roles of water is essential to understanding the function of membrane proteins.
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Affiliation(s)
- Tivadar Orban
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA
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15
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Abstract
Various methods of protein footprinting use hydrogen peroxide as an oxidant. Its removal by various solid-phase desalting methods, catalase treatment, or freeze drying after the footprinting is critical to ensure no uncontrolled oxidation. Although catalase treatment removes hydrogen peroxide with little loss of protein or additional protein oxidation, we discovered that freeze drying or freezing of the protein in a peroxide solution does lead to protein oxidation. Interestingly, the oxidation is not a result of freeze or thaw processes but is dependent on the temperature and length of time for incubation. After 2 h, apomyoglobin undergoes almost-complete single oxidation at -80 degrees C and double oxidation at -15 degrees C. Minimal oxidation is observed at 4 and 22 degrees C, compared to oxidation at -80 or -15 degrees C. The concentration of hydrogen peroxide is critical; 75 mM (0.2%) is required to oxidize >50% of the protein at -15 degrees C and 100 mM (0.3%) is required at -80 degrees C. In addition to Met, approximately 5% of the tryptophan and tyrosine residues are oxidized, as well as lower amounts of His and Phe. Oxidation of Val 68 and Val 17 (a buried residue) also occurs, with the oxidation of Val 17 likely occurring by electron transfer from one of two of the oxidized aromatic residues that are in contact with Val 17. Here, we describe the need to remove the hydrogen peroxide prior to cold storage of proteins, and we also report some preliminary results pertaining to the mechanism of cold, solid-state oxidation.
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Affiliation(s)
- David M Hambly
- Department of Chemistry, Washington University in St. Louis, Missouri 63130, USA
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16
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Spraggins JM, Lloyd JA, Johnston MV, Laskin J, Ridge DP. Fragmentation mechanisms of oxidized peptides elucidated by SID, RRKM modeling, and molecular dynamics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1579-1592. [PMID: 19560936 DOI: 10.1016/j.jasms.2009.04.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 03/06/2009] [Accepted: 04/20/2009] [Indexed: 05/28/2023]
Abstract
The gas-phase fragmentation reactions of singly charged angiotensin II (AngII, DR(+)VYIHPF) and the ozonolysis products AngII+O (DR(+)VY*IHPF), AngII+3O (DR(+)VYIH*PF), and AngII+4O (DR(+)VY*IH*PF) were studied using SID FT-ICR mass spectrometry, RRKM modeling, and molecular dynamics. Oxidation of Tyr (AngII+O) leads to a low-energy charge-remote selective fragmentation channel resulting in the b(4)+O fragment ion. Modification of His (AngII+3O and AngII+4O) leads to a series of new selective dissociation channels. For AngII+3O and AngII+4O, the formation of [MH+3O](+)-45 and [MH+3O](+)-71 are driven by charge-remote processes while it is suggested that b(5) and [MH+3O](+)-88 fragments are a result of charge-directed reactions. Energy-resolved SID experiments and RRKM modeling provide threshold energies and activation entropies for the lowest energy fragmentation channel for each of the parent ions. Fragmentation of the ozonolysis products was found to be controlled by entropic effects. Mechanisms are proposed for each of the new dissociation pathways based on the energies and entropies of activation and parent ion conformations sampled using molecular dynamics.
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Affiliation(s)
- Jeffrey M Spraggins
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
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17
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Fitzgerald MC, West GM. Painting proteins with covalent labels: what's in the picture? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1193-1206. [PMID: 19269190 DOI: 10.1016/j.jasms.2009.02.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 02/06/2009] [Accepted: 02/09/2009] [Indexed: 05/27/2023]
Abstract
Knowledge about the structural and biophysical properties of proteins when they are free in solution and/or in complexes with other molecules is essential for understanding the biological processes that proteins regulate. Such knowledge is also important to drug discovery efforts, particularly those focused on the development of therapeutic agents with protein targets. In the last decade a variety of different covalent labeling techniques have been used in combination with mass spectrometry to probe the solution-phase structures and biophysical properties of proteins and protein-ligand complexes. Highlighted here are five different mass spectrometry-based covalent labeling strategies including: continuous hydrogen/deuterium (H/D) exchange labeling, hydroxyl radical-mediated footprinting, SUPREX (stability of unpurified proteins from rates of H/D exchange), PLIMSTEX (protein-ligand interaction by mass spectrometry, titration, and H/D exchange), and SPROX (stability of proteins from rates of oxidation). The basic experimental protocols used in each of the above-cited methods are summarized along with the kind of biophysical information they generate. Also discussed are the relative strengths and weaknesses of the different methods for probing the wide range of conformational states that proteins and protein-ligand complexes can adopt when they are in solution.
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Affiliation(s)
- Michael C Fitzgerald
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, USA.
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18
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Watson C, Janik I, Zhuang T, Charvátová O, Woods RJ, Sharp JS. Pulsed electron beam water radiolysis for submicrosecond hydroxyl radical protein footprinting. Anal Chem 2009; 81:2496-505. [PMID: 19265387 DOI: 10.1021/ac802252y] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydroxyl radical footprinting is a valuable technique for studying protein structure, but care must be taken to ensure that the protein does not unfold during the labeling process due to oxidative damage. Footprinting methods based on submicrosecond laser photolysis of peroxide that complete the labeling process faster than the protein can unfold have been recently described; however, the mere presence of large amounts of hydrogen peroxide can also cause uncontrolled oxidation and minor conformational changes. We have developed a novel method for submicrosecond hydroxyl radical protein footprinting using a pulsed electron beam from a 2 MeV Van de Graaff electron accelerator to generate a high concentration of hydroxyl radicals by radiolysis of water. The amount of oxidation can be controlled by buffer composition, pulsewidth, dose, and dissolved nitrous oxide gas in the sample. Our results with ubiquitin and beta-lactoglobulin A demonstrate that one submicrosecond electron beam pulse produces extensive protein surface modifications. Highly reactive residues that are buried within the protein structure are not oxidized, indicating that the protein retains its folded structure during the labeling process. Time-resolved spectroscopy indicates that the major part of protein oxidation is complete in a time scale shorter than that of large scale protein motions.
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Affiliation(s)
- Caroline Watson
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA
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19
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Running WE, Reilly JP. Ribosomal Proteins of Deinococcus radiodurans: Their Solvent Accessibility and Reactivity. J Proteome Res 2009; 8:1228-46. [DOI: 10.1021/pr800544y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- William E. Running
- Department of Chemistry, Indiana University, Bloomington, Indiana, 47405
| | - James P. Reilly
- Department of Chemistry, Indiana University, Bloomington, Indiana, 47405
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20
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Danielsson J, Liljedahl L, Bárány-Wallje E, Sønderby P, Kristensen LH, Martinez-Yamout MA, Dyson HJ, Wright PE, Poulsen FM, Mäler L, Gräslund A, Kragelund BB. The intrinsically disordered RNR inhibitor Sml1 is a dynamic dimer. Biochemistry 2009; 47:13428-37. [PMID: 19086274 DOI: 10.1021/bi801040b] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sml1 is a small ribonucleotide reductase (RNR) regulatory protein in Saccharomyces cerevisiae that binds to and inhibits RNR activation. NMR studies of 15N-labeled Sml1 (104 residues), as well as of a truncated variant (residues 50-104), have allowed characterization of their molecular properties. Sml1 belongs to the class of intrinsically disordered proteins with a high degree of dynamics and very little stable structure. Earlier suggestions for a dimeric structure of Sml1 were confirmed, and from translation diffusion NMR measurements, a dimerization dissociation constant of 0.1 mM at 4 degreesC could be determined. The hydrodynamic radius for the monomeric form of Sml1 was determined to be 23.4 A, corresponding to a protein size between those of a globular protein and a coil. Formation of a dimer results in a hydrodynamic radius of 34.4 A. The observed chemical shifts showed in agreement with previous studies two segments with transient helical structure, residues 4-20 and 60-86, and relaxation studies clearly showed restricted motion in these segments. A spin-label attached to C14 showed long-range interactions with residues 60-70 and 85-95, suggesting that the N-terminal domain folds onto the C-terminal domain. Importantly, protease degradation studies combined with mass spectrometry indicated that the N-terminal domain is degraded before the C-terminal region and thus may serve as a protection against proteolysis of the functionally important C-terminal region. Dimer formation was not associated with significant induction of structure but was found to provide further protection against proteolysis. We propose that this molecular shielding and protection of vital functional structures from degradation by functionally unimportant sites may be a general attribute of other natively disordered proteins.
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Affiliation(s)
- Jens Danielsson
- Department of Biochemistry and Biophysics, Stockholm University, S-106 91 Stockholm, Sweden
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21
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Charvátová O, Foley BL, Bern MW, Sharp JS, Orlando R, Woods RJ. Quantifying protein interface footprinting by hydroxyl radical oxidation and molecular dynamics simulation: application to galectin-1. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:1692-705. [PMID: 18707901 PMCID: PMC2607067 DOI: 10.1016/j.jasms.2008.07.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 07/10/2008] [Accepted: 07/14/2008] [Indexed: 05/13/2023]
Abstract
Biomolecular surface mapping methods offer an important alternative method for characterizing protein-protein and protein-ligand interactions in cases in which it is not possible to determine high-resolution three-dimensional (3D) structures of complexes. Hydroxyl radical footprinting offers a significant advance in footprint resolution compared with traditional chemical derivatization. Here we present results of footprinting performed with hydroxyl radicals generated on the nanosecond time scale by laser-induced photodissociation of hydrogen peroxide. We applied this emerging method to a carbohydrate-binding protein, galectin-1. Since galectin-1 occurs as a homodimer, footprinting was employed to characterize the interface of the monomeric subunits. Efficient analysis of the mass spectrometry data for the oxidized protein was achieved with the recently developed ByOnic (Palo Alto, CA) software that was altered to handle the large number of modifications arising from side-chain oxidation. Quantification of the level of oxidation has been achieved by employing spectral intensities for all of the observed oxidation states on a per-residue basis. The level of accuracy achievable from spectral intensities was determined by examination of mixtures of synthetic peptides related to those present after oxidation and tryptic digestion of galectin-1. A direct relationship between side-chain solvent accessibility and level of oxidation emerged, which enabled the prediction of the level of oxidation given the 3D structure of the protein. The precision of this relationship was enhanced through the use of average solvent accessibilities computed from 10 ns molecular dynamics simulations of the protein.
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Affiliation(s)
- Olga Charvátová
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, Georgia, 30602, USA
| | - B. Lachele Foley
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, Georgia, 30602, USA
| | - Marshall W. Bern
- Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, California, 94304, USA
| | - Joshua S. Sharp
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, Georgia, 30602, USA
| | - Ron Orlando
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, Georgia, 30602, USA
| | - Robert J. Woods
- Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Rd, Athens, Georgia, 30602, USA
- Correspondence to : Robert J. Woods, , Phone: +1-706-542-4454, FAX : +1-706-542-4412
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22
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McClintock C, Kertesz V, Hettich RL. Development of an Electrochemical Oxidation Method for Probing Higher Order Protein Structure with Mass Spectrometry. Anal Chem 2008; 80:3304-17. [DOI: 10.1021/ac702493a] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Carlee McClintock
- Graduate School of Genome Science and Technology, University of TennesseeOak Ridge National Laboratory, 1060 Commerce Park, Oak Ridge, Tennessee 37830, and Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS 6131, Oak Ridge, Tennessee 37831
| | - Vilmos Kertesz
- Graduate School of Genome Science and Technology, University of TennesseeOak Ridge National Laboratory, 1060 Commerce Park, Oak Ridge, Tennessee 37830, and Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS 6131, Oak Ridge, Tennessee 37831
| | - Robert L. Hettich
- Graduate School of Genome Science and Technology, University of TennesseeOak Ridge National Laboratory, 1060 Commerce Park, Oak Ridge, Tennessee 37830, and Chemical Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS 6131, Oak Ridge, Tennessee 37831
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23
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Hnízda A, Santrůcek J, Sanda M, Strohalm M, Kodícek M. Reactivity of histidine and lysine side-chains with diethylpyrocarbonate -- a method to identify surface exposed residues in proteins. ACTA ACUST UNITED AC 2007; 70:1091-7. [PMID: 17765977 DOI: 10.1016/j.jbbm.2007.07.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 07/13/2007] [Accepted: 07/15/2007] [Indexed: 11/22/2022]
Abstract
The chemical modification of amino acid side-chains followed by mass spectrometric detection can reveal at least partial information about the 3-D structure of proteins. In this work we tested diethylpyrocarbonate, as a common histidyl modification agent, for this purpose. Appropriate conditions for the reaction and detection of modified amino acids were developed using angiotensin II as a model peptide. We studied the modification of several model proteins with a known spatial arrangement (insulin, cytochrome c, lysozyme and human serum albumin). Our results revealed that the surface accessibility of residues is a necessary, although in itself insufficient, condition for their reactivity; the microenvironment of side-chains and the dynamics of protein structure also affect the ability of residues to react. However the detection of modified residues can be taken as proof of their surface accessibility, and of direct contact with solvent molecules.
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Affiliation(s)
- Ales Hnízda
- Institute of Inherited Metabolic Disorders, 1st School of Medicine, Charles University, 128 00 Praha 2, Czech Republic
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24
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Kamal JKA, Benchaar SA, Takamoto K, Reisler E, Chance MR. Three-dimensional structure of cofilin bound to monomeric actin derived by structural mass spectrometry data. Proc Natl Acad Sci U S A 2007; 104:7910-5. [PMID: 17470807 PMCID: PMC1876546 DOI: 10.1073/pnas.0611283104] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytoskeletal protein, actin, has its structure and function regulated by cofilin. In the absence of an atomic resolution structure for the actin/cofilin complex, the mechanism of cofilin regulation is poorly understood. Theoretical studies based on the similarities of cofilin and gelsolin segment 1 proposed the cleft between subdomains 1 and 3 in actin as the cofilin binding site. We used radiolytic protein footprinting with mass spectrometry and molecular modeling to provide an atomic model of how cofilin binds to monomeric actin. Footprinting data suggest that cofilin binds to the cleft between subdomains 1 and 2 in actin and that cofilin induces further closure of the actin nucleotide cleft. Site-specific fluorescence data confirm these results. The model identifies key ionic and hydrophobic interactions at the binding interface, including hydrogen-bonding between His-87 of actin to Ser-89 of cofilin that may control the charge dependence of cofilin binding. This model and its implications fill an especially important niche in the actin field, owing to the fact that ongoing crystallization efforts of the actin/cofilin complex have so far failed. This 3D binary complex structure is derived from a combination of solution footprinting data and computational approaches and outlines a general method for determining the structure of such complexes.
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Affiliation(s)
- J. K. Amisha Kamal
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
| | - Sabrina A. Benchaar
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095
| | - Keiji Takamoto
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
| | - Emil Reisler
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095
| | - Mark R. Chance
- *Center for Proteomics, Case Western Reserve University School of Medicine, Cleveland, OH 44106; and
- To whom correspondence should be addressed. E-mail:
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25
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Takamoto K, Kamal JKA, Chance MR. Biochemical implications of a three-dimensional model of monomeric actin bound to magnesium-chelated ATP. Structure 2007; 15:39-51. [PMID: 17223531 DOI: 10.1016/j.str.2006.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 11/06/2006] [Accepted: 11/18/2006] [Indexed: 11/19/2022]
Abstract
Actin structure is of intense interest in biology due to its importance in cell function and motility mediated by the spatial and temporal regulation of actin monomer-filament interconversions in a wide range of developmental and disease states. Despite this interest, the structure of many functionally important actin forms has eluded high-resolution analysis. Due to the propensity of actin monomers to assemble into filaments structural analysis of Mg-bound actin monomers has proven difficult, whereas high-resolution structures of actin with a diverse array of ligands that preclude polymerization have been quite successful. In this work, we provide a high-resolution structural model of the Mg-ATP-actin monomer using a combination of computational methods and experimental footprinting data that we have previously published. The key conclusion of this study is that the structure of the nucleotide binding cleft defined by subdomains 2 and 4 is essentially closed, with specific contacts between two subdomains predicted by the data.
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Affiliation(s)
- Keiji Takamoto
- Case Center for Proteomics, Case Western Reserve University, 10090 Euclid Avenue, Cleveland, OH 44106, USA.
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26
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Sharp JS, Tomer KB. Analysis of the oxidative damage-induced conformational changes of apo- and holocalmodulin by dose-dependent protein oxidative surface mapping. Biophys J 2006; 92:1682-92. [PMID: 17158574 PMCID: PMC1796823 DOI: 10.1529/biophysj.106.099093] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Calmodulin (CaM) is known to undergo conformational and functional changes on oxidation, allowing CaM to function as an oxidative stress sensor. We report the use of a novel mass spectrometry-based methodology to monitor the structure of apo- and holo-CaM as it undergoes conformational changes as a result of increasing amounts of oxidative damage. The kinetics of oxidation for eight peptides are followed by mass spectrometry, and 12 sites of oxidation are determined by MS/MS. Changes in the pseudo-first-order rate constant of oxidation for a peptide after increasing radiation exposure reveal changes in the accessibility of the peptide to the diffusing hydroxyl radical, indicating conformational changes as a function of increased oxidative damage. For holo-CaM, most sites rapidly become less exposed to hydroxyl radicals as the protein accumulates oxidative damage, indicating a closing of the hydrophobic pockets in the N- and C-terminal lobes. For apo-CaM, many of the sites rapidly become more exposed until they resemble the solvent accessibility of holo-CaM in the native structure and then rapidly become more buried, mimicking the conformational changes of holo-CaM. At the most heavily damaged points measured, the rates of oxidation for both apo- and holo-CaM are essentially identical, suggesting the two assume similar structures.
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Affiliation(s)
- Joshua S Sharp
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
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27
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Williams JG, Tomer KB, Hioe CE, Zolla-Pazner S, Norris PJ. The antigenic determinants on HIV p24 for CD4+ T cell inhibiting antibodies as determined by limited proteolysis, chemical modification, and mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1560-1569. [PMID: 16875837 DOI: 10.1016/j.jasms.2006.06.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 06/18/2006] [Accepted: 06/19/2006] [Indexed: 05/11/2023]
Abstract
In the last decade, mass spectrometry has been employed by more and more researchers for identifying the proteins in a macromolecular complex as well as for defining the surfaces of their binding interfaces. This characterization of protein-protein interfaces usually involves at least one of several different methodologies in addition to the actual mass spectrometry. For example, limited proteolysis is often used as a first step in defining regions of a protein that are protected from proteolysis when the protein of interest is part of a macromolecular complex. Other techniques used in conjunction with mass spectrometry for determining regions of a protein involved in protein-protein interactions include chemical modification, such as covalent cross-linking, acetylation of lysines, hydrogen-deuterium exchange, or other forms of modification. In this report, both limited proteolysis and chemical modification were combined with several mass spectrometric techniques in efforts to define the protein surface on the HIV core protein, p24, recognized by two different monoclonal human antibodies that were isolated from HIV+ patients. One of these antibodies, 1571, strongly inhibits the CD4+ T cell proliferative response to a known epitope (PEVIPMFSALSEGATP), while the other antibody, 241-D, does not inhibit as strongly. The epitopes for both of these antibodies were determined to be discontinuous and localized to the N-terminus of p24. Interestingly, the epitope recognized by the strongly inhibiting antibody, 1571, completely overlaps the T cell epitope PEVIPMFSALSEGATP, while the antibody 241-D binds to a region adjacent to the region of p24 recognized by the antibody 1571. These results suggest that, possibly due to epitope competition, antibodies produced during HIV infection can negatively affect CD4+ T cell-mediated immunity against the virus.
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Affiliation(s)
- Jason G Williams
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Laboratory of Structural Biology, 111 TW Alexander Drive, MD F0-03, 27709, Research Triangle Park, NC, USA
| | - Kenneth B Tomer
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Laboratory of Structural Biology, 111 TW Alexander Drive, MD F0-03, 27709, Research Triangle Park, NC, USA.
| | - Catarina E Hioe
- New York Veterans Affairs Medical Center and Department of Pathology, New York University School of Medicine, New York, New York, USA
| | - Susan Zolla-Pazner
- New York Veterans Affairs Medical Center and Department of Pathology, New York University School of Medicine, New York, New York, USA
| | - Philip J Norris
- Blood Systems Research Institute and Departments of Laboratory Medicine and Medicine, University of California-San Francisco, San Francisco, California, USA
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28
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Takamoto K, Chance MR. RADIOLYTIC PROTEIN FOOTPRINTING WITH MASS SPECTROMETRY TO PROBE THE STRUCTURE OF MACROMOLECULAR COMPLEXES. ACTA ACUST UNITED AC 2006; 35:251-76. [PMID: 16689636 DOI: 10.1146/annurev.biophys.35.040405.102050] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Structural proteomics approaches using mass spectrometry are increasingly used in biology to examine the composition and structure of macromolecules. Hydroxyl radical-mediated protein footprinting using mass spectrometry has recently been developed to define structure, assembly, and conformational changes of macromolecules in solution based on measurements of reactivity of amino acid side chain groups with covalent modification reagents. Accurate measurements of side chain reactivity are achieved using quantitative liquid-chromatography-coupled mass spectrometry, whereas the side chain modification sites are identified using tandem mass spectrometry. In addition, the use of footprinting data in conjunction with computational modeling approaches is a powerful new method for testing and refining structural models of macromolecules and their complexes. In this review, we discuss the basic chemistry of hydroxyl radical reactions with peptides and proteins, highlight various approaches to map protein structure using radical oxidation methods, and describe state-of-the-art approaches to combine computational and footprinting data.
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Affiliation(s)
- Keiji Takamoto
- Case Center for Proteomics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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29
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Sharp JS, Tomer KB. Effects of Anion Proximity in Peptide Primary Sequence on the Rate and Mechanism of Leucine Oxidation. Anal Chem 2006; 78:4885-93. [PMID: 16841907 DOI: 10.1021/ac060329o] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Hydroxyl radical surface mapping is a useful tool for investigating protein structure and folding. The rate of protein side-chain oxidation by the hydroxyl radical is known to be affected primarily by the chemical reactivity of the side chain and the accessibility of the reactive site to the radical. Efforts have been made to determine the inherent rate of stable product formation of each amino acid side chain, so that the rate of oxidation of an amino acid can be used to accurately estimate the average solvent accessibility of the amino acid side chain in the folded protein. However, the effects of nearby primary sequence on peptide oxidation have not been studied. Here, we examine the amounts of various oxidation products of a small peptide consisting of one leucine and one aspartic acid separated by zero to five glycine residues, as well as with modification of the N- and C-terminus. We find that the relative amounts of certain oxidation products can be heavily influenced by the primary structure of the surrounding peptide. The formation of many products, including hydroxylation, is inhibited by proximity to negative charges, while the formation of other products showed more complicated responses to changing primary sequence.
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Affiliation(s)
- Joshua S Sharp
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA.
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30
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Guan JQ, Chance MR. Structural proteomics of macromolecular assemblies using oxidative footprinting and mass spectrometry. Trends Biochem Sci 2005; 30:583-92. [PMID: 16126388 DOI: 10.1016/j.tibs.2005.08.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 07/14/2005] [Accepted: 08/16/2005] [Indexed: 11/20/2022]
Abstract
Understanding the composition, structure and dynamics of macromolecules and their assemblies is at the forefront of biological science today. Hydroxyl-radical-mediated protein footprinting using mass spectrometry can define macromolecular structure, macromolecular assembly and conformational changes of macromolecules in solution based on measurements of reactivity of amino acid side-chain groups with covalent-modification reagents. Subsequent to oxidation by reactive oxygen species, proteins are digested by specific proteases to generate peptides for analysis by mass spectrometry. Accurate measurements of side-chain reactivity are achieved using quantitative liquid-chromatography-coupled mass spectrometry, whereas the side-chain sites within the macromolecular probes are identified using tandem mass spectrometry. In addition, the use of footprinting data in conjunction with computational modeling approaches is a powerful new method for testing and refining structural models of macromolecules and their complexes.
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Affiliation(s)
- Jing-Qu Guan
- Case Center for Proteomics and Mass Spectrometry, 930 BRB, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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31
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Xu G, Liu R, Zak O, Aisen P, Chance MR. Structural allostery and binding of the transferrin*receptor complex. Mol Cell Proteomics 2005; 4:1959-67. [PMID: 16332734 DOI: 10.1074/mcp.m500095-mcp200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The structural allostery and binding interface for the human serum transferrin (Tf)*transferrin receptor (TfR) complex were identified using radiolytic footprinting and mass spectrometry. We have determined previously that the transferrin C-lobe binds to the receptor helical domain. In this study we examined the binding interactions of full-length transferrin with receptor and compared these data with a model of the complex derived from cryoelectron microscopy (cryo-EM) reconstructions (Cheng, Y., Zak, O., Aisen, P., Harrison, S. C. & Walz, T. (2004) Structure of the human transferrin receptor.transferrin complex. Cell 116, 565-576). The footprinting results provide the following novel conclusions. First, we report characteristic oxidations of acidic residues in the C-lobe of native Tf and basic residues in the helical domain of TfR that were suppressed as a function of complex formation; this confirms ionic interactions between these protein segments as predicted by cryo-EM data and demonstrates a novel method for detecting ion pair interactions in the formation of macromolecular complexes. Second, the specific side-chain interactions between the C-lobe and N-lobe of transferrin and the corresponding interactions sites on the transferrin receptor predicted from cryo-EM were confirmed in solution. Last, the footprinting data revealed allosteric movements of the iron binding C- and N-lobes of Tf that sequester iron as a function of complex formation; these structural changes promote tighter binding of the metal ion and facilitate efficient ion transport during endocytosis.
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Affiliation(s)
- Guozhong Xu
- Case Center for Proteomics and Mass Spectrometry, Case Western Reserve University, Cleveland, Ohio 44106, USA
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