1
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Lin Y, Gross ML. Mass Spectrometry-Based Structural Proteomics for Metal Ion/Protein Binding Studies. Biomolecules 2022; 12:135. [PMID: 35053283 PMCID: PMC8773722 DOI: 10.3390/biom12010135] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 01/01/2023] Open
Abstract
Metal ions are critical for the biological and physiological functions of many proteins. Mass spectrometry (MS)-based structural proteomics is an ever-growing field that has been adopted to study protein and metal ion interactions. Native MS offers information on metal binding and its stoichiometry. Footprinting approaches coupled with MS, including hydrogen/deuterium exchange (HDX), "fast photochemical oxidation of proteins" (FPOP) and targeted amino-acid labeling, identify binding sites and regions undergoing conformational changes. MS-based titration methods, including "protein-ligand interactions by mass spectrometry, titration and HD exchange" (PLIMSTEX) and "ligand titration, fast photochemical oxidation of proteins and mass spectrometry" (LITPOMS), afford binding stoichiometry, binding affinity, and binding order. These MS-based structural proteomics approaches, their applications to answer questions regarding metal ion protein interactions, their limitations, and recent and potential improvements are discussed here. This review serves as a demonstration of the capabilities of these tools and as an introduction to wider applications to solve other questions.
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Affiliation(s)
- Yanchun Lin
- Department of Chemistry, 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
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2
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James EI, Murphree TA, Vorauer C, Engen JR, Guttman M. Advances in Hydrogen/Deuterium Exchange Mass Spectrometry and the Pursuit of Challenging Biological Systems. Chem Rev 2021; 122:7562-7623. [PMID: 34493042 PMCID: PMC9053315 DOI: 10.1021/acs.chemrev.1c00279] [Citation(s) in RCA: 95] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
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Solution-phase hydrogen/deuterium
exchange (HDX) coupled to mass
spectrometry (MS) is a widespread tool for structural analysis across
academia and the biopharmaceutical industry. By monitoring the exchangeability
of backbone amide protons, HDX-MS can reveal information about higher-order
structure and dynamics throughout a protein, can track protein folding
pathways, map interaction sites, and assess conformational states
of protein samples. The combination of the versatility of the hydrogen/deuterium
exchange reaction with the sensitivity of mass spectrometry has enabled
the study of extremely challenging protein systems, some of which
cannot be suitably studied using other techniques. Improvements over
the past three decades have continually increased throughput, robustness,
and expanded the limits of what is feasible for HDX-MS investigations.
To provide an overview for researchers seeking to utilize and derive
the most from HDX-MS for protein structural analysis, we summarize
the fundamental principles, basic methodology, strengths and weaknesses,
and the established applications of HDX-MS while highlighting new
developments and applications.
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Affiliation(s)
- Ellie I James
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Taylor A Murphree
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Clint Vorauer
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - John R Engen
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
| | - Miklos Guttman
- Department of Medicinal Chemistry, University of Washington, Seattle, Washington 98195, United States
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3
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McKenzie-Coe A, Shortt R, Jones LM. THE MAKING OF A FOOTPRINT IN PROTEIN FOOTPRINTING: A REVIEW IN HONOR OF MICHAEL L. GROSS. MASS SPECTROMETRY REVIEWS 2021; 40:177-200. [PMID: 32400038 PMCID: PMC7849054 DOI: 10.1002/mas.21632] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/17/2020] [Accepted: 04/23/2020] [Indexed: 06/11/2023]
Abstract
Within the past decade protein footprinting in conjunction with mass spectrometry has become a powerful and versatile means to unravel the higher order structure of proteins. Footprinting-based approaches has demonstrated the capacity to inform on interaction sites and dynamic regions that participate in conformational changes. These findings when set in a biological perspective inform on protein folding/unfolding, protein-protein interactions, and protein-ligand interactions. In this review, we will look at the contribution of Dr. Michael L. Gross to protein footprinting approaches such as hydrogen deuterium exchange mass spectrometry and hydroxyl radical protein footprinting. This review details the development of novel footprinting methods as well as their applications to study higher order protein structure. © 2020 The Authors. Mass Spectrometry Reviews published by John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Alan McKenzie-Coe
- Department of Pharmaceutical Sciences, University of Maryland Baltimore, Baltimore, Maryland, 21201
| | - Raquel Shortt
- Department of Pharmaceutical Sciences, University of Maryland Baltimore, Baltimore, Maryland, 21201
| | - Lisa M Jones
- Department of Pharmaceutical Sciences, University of Maryland Baltimore, Baltimore, Maryland, 21201
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4
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Minnes L, Greetham GM, Shaw DJ, Clark IP, Fritzsch R, Towrie M, Parker AW, Henry AJ, Taylor RJ, Hunt NT. Uncovering the Early Stages of Domain Melting in Calmodulin with Ultrafast Temperature-Jump Infrared Spectroscopy. J Phys Chem B 2019; 123:8733-8739. [PMID: 31557034 PMCID: PMC7007250 DOI: 10.1021/acs.jpcb.9b08870] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
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The signaling protein
calmodulin (CaM) undergoes a well-known change
in secondary structure upon binding Ca2+, but the structural
plasticity of the Ca2+-free apo state
is linked to CaM functionality. Variable temperature studies of apo-CaM indicate two structural transitions at 46 and 58
°C that are assigned to melting of the C- and N-terminal domains,
respectively, but the molecular mechanism of domain unfolding is unknown.
We report temperature-jump time-resolved infrared (IR) spectroscopy
experiments designed to target the first steps in the C-terminal domain
melting transition of human apo-CaM. A comparison
of the nonequilibrium relaxation of apo-CaM with
the more thermodynamically stable holo-CaM, with
4 equiv of Ca2+ bound, shows that domain melting of apo-CaM begins on microsecond time scales with α-helix
destabilization. These observations enable the assignment of previously
reported dynamics of CaM on hundreds of microsecond time scales to
thermally activated melting, producing a complete mechanism for thermal
unfolding of CaM.
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Affiliation(s)
- Lucy Minnes
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , United Kingdom
| | - Gregory M Greetham
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | | | - Ian P Clark
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | - Robby Fritzsch
- Department of Physics, SUPA , University of Strathclyde , Glasgow G4 0NG , United Kingdom
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | - Anthony W Parker
- STFC Central Laser Facility, Research Complex at Harwell , Rutherford Appleton Laboratory , Harwell Campus , Didcot OX11 0QX , United Kingdom
| | | | | | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute , University of York , Heslington, York YO10 5DD , United Kingdom
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5
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Liu XR, Zhang MM, Rempel DL, Gross ML. A Single Approach Reveals the Composite Conformational Changes, Order of Binding, and Affinities for Calcium Binding to Calmodulin. Anal Chem 2019; 91:5508-5512. [PMID: 30963760 DOI: 10.1021/acs.analchem.9b01062] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We found that a newly developed method named LITPOMS (ligand titration, fast photochemical oxidation of proteins and mass spectrometry) can characterize section-by-section of a protein the conformational changes induced by metal-ion binding. Peptide-level LITPOMS applied to Ca2+ binding to calmodulin reveals binding order and site-specific affinity, providing new insights on the behavior of proteins upon binding Ca2+. We established that EF hand-4 (EF-4) binds calcium first, followed by EF-3, EF-2, and EF-1 and determined the four affinity constants by modeling the extent-of-modification curves. We also found positive cooperativity between EF-4, EF-3 and EF-2, EF-1 and allostery involving the four EF-hands. LITPOMS recapitulates via one approach the calcium-calmodulin binding that required decades of sophisticated development to afford versatility, comprehensiveness, and outstanding spatial resolution.
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Affiliation(s)
- Xiaoran Roger Liu
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Mengru Mira Zhang
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Don L Rempel
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
| | - Michael L Gross
- Department of Chemistry , Washington University in St. Louis , One Brookings Drive , St. Louis , Missouri 63130 , United States
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6
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Minnes L, Shaw DJ, Cossins BP, Donaldson PM, Greetham GM, Towrie M, Parker AW, Baker MJ, Henry AJ, Taylor RJ, Hunt NT. Quantifying Secondary Structure Changes in Calmodulin Using 2D-IR Spectroscopy. Anal Chem 2017; 89:10898-10906. [DOI: 10.1021/acs.analchem.7b02610] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Lucy Minnes
- Department
of Physics, University of Strathclyde, SUPA, 107 Rottenrow East, Glasgow, G4 0NG, United Kingdom
| | | | | | - Paul M. Donaldson
- STFC
Central Laser Facility, Research Complex at Harwell, Rutherford Appleton
Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, United Kingdom
| | - Gregory M. Greetham
- STFC
Central Laser Facility, Research Complex at Harwell, Rutherford Appleton
Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, United Kingdom
| | - Michael Towrie
- STFC
Central Laser Facility, Research Complex at Harwell, Rutherford Appleton
Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, United Kingdom
| | - Anthony W. Parker
- STFC
Central Laser Facility, Research Complex at Harwell, Rutherford Appleton
Laboratory, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, United Kingdom
| | - Matthew J. Baker
- WestCHEM,
Department of Pure and Applied Chemistry, Technology and Innovation
Centre, University of Strathclyde, 99 George Street, Glasgow, G1 1RD, United Kingdom
| | | | | | - Neil T. Hunt
- Department
of Physics, University of Strathclyde, SUPA, 107 Rottenrow East, Glasgow, G4 0NG, United Kingdom
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7
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Susa AC, Xia Z, Williams ER. Small Emitter Tips for Native Mass Spectrometry of Proteins and Protein Complexes from Nonvolatile Buffers That Mimic the Intracellular Environment. Anal Chem 2017; 89:3116-3122. [DOI: 10.1021/acs.analchem.6b04897] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Anna C. Susa
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
| | - Zijie Xia
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
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8
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Susa AC, Xia Z, Tang HYH, Tainer JA, Williams ER. Charging of Proteins in Native Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:332-340. [PMID: 27734326 PMCID: PMC5283922 DOI: 10.1007/s13361-016-1517-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 09/22/2016] [Accepted: 09/27/2016] [Indexed: 05/19/2023]
Abstract
Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo proton transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the protein ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism. Graphical Abstract ᅟ.
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Affiliation(s)
- Anna C Susa
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Zijie Xia
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Henry Y H Tang
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - John A Tainer
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77030, USA
| | - Evan R Williams
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA.
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9
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Miladi M, Olaitan AD, Zekavat B, Solouki T. Competing noncovalent host-guest interactions and H/D exchange: reactions of benzyloxycarbonyl-proline glycine dipeptide variants with ND3. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:1938-1949. [PMID: 26289383 DOI: 10.1007/s13361-015-1218-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 05/26/2015] [Accepted: 06/17/2015] [Indexed: 06/04/2023]
Abstract
A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ᅟ.
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Affiliation(s)
- Mahsan Miladi
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76706, USA
| | - Abayomi D Olaitan
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76706, USA
| | - Behrooz Zekavat
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76706, USA
| | - Touradj Solouki
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76706, USA.
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10
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Cassou CA, Williams ER. Desalting protein ions in native mass spectrometry using supercharging reagents. Analyst 2015; 139:4810-9. [PMID: 25133273 DOI: 10.1039/c4an01085j] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Effects of the supercharging reagents m-NBA and sulfolane on sodium ion adduction to protein ions formed using native mass spectrometry were investigated. There is extensive sodium adduction on protein ions formed by electrospray ionization from aqueous solutions containing millimolar concentrations of NaCl, which can lower sensitivity by distributing the signal of a given charge state over multiple adducted ions and can reduce mass measuring accuracy for large proteins and non-covalent complexes for which individual adducts cannot be resolved. The average number of sodium ions adducted to the most abundant ion formed from ten small (8.6-29 kDa) proteins for which adducts can be resolved is reduced by 58% or 80% on average, respectively, when 1.5% m-NBA or 2.5% sulfolane are added to aqueous solutions containing sodium compared to without the supercharging reagent. Sulfolane is more effective than m-NBA at reducing sodium ion adduction and at preserving non-covalent protein-ligand and protein-protein interactions. Desalting with 2.5% sulfolane enables detection of several glycosylated forms of 79.7 kDa holo-transferrin and NADH bound to the 146 kDa homotetramer LDH, which are otherwise unresolved due to peak broadening from extensive sodium adduction. Although sulfolane is more effective than m-NBA at protein ion desalting, m-NBA reduces salt clusters at high m/z and can increase the signal-to-noise ratios of protein ions by reducing chemical noise. Desalting is likely a result of these supercharging reagents binding sodium ions in solution, thereby reducing the sodium available to adduct to protein ions.
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Affiliation(s)
- Catherine A Cassou
- Department of Chemistry, University of California, B42 Hildebrand Hall, Berkeley, California 94720-1460, USA.
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11
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Gülbakan B, Barylyuk K, Zenobi R. Determination of thermodynamic and kinetic properties of biomolecules by mass spectrometry. Curr Opin Biotechnol 2015; 31:65-72. [DOI: 10.1016/j.copbio.2014.08.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/08/2014] [Accepted: 08/12/2014] [Indexed: 01/13/2023]
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12
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Susa AC, Mortensen DN, Williams ER. Effects of cations on protein and peptide charging in electrospray ionization from aqueous solutions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:918-27. [PMID: 24729190 PMCID: PMC4051497 DOI: 10.1007/s13361-014-0864-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 02/12/2014] [Accepted: 02/18/2014] [Indexed: 05/11/2023]
Abstract
The effects of eight different cations with ionic radii between 69 and 337 pm on the charging of peptides and proteins with electrospray ionization from aqueous acetate salt solutions are reported. Significant adduction occurs for all cations except NH4(+), and the average protein charge is lower when formed from solutions containing salts compared with solutions without salts added. Circular dichroism and ion mobility results show the protein conformations are different in pure water compared with salt solutions, which likely affects the extent of charging. The average charge of protein and peptide ions formed from solutions with Li(+) and Cs(+), which have Gibbs solvation free energies (GSFEs) that differ by 225 kJ/mol, is similar. Lower charge states are typically formed from solutions with tetramethylammonium and tetraethylammonium that have lower GSFE values. Loss of the larger cations that have the lowest GSFEs is facile when adducted protein ions are collisionally activated, resulting in the formation of lower analyte charge states. This reaction pathway provides a route to produce abundant singly protonated protein ions under native mass spectrometry conditions. The average protein and peptide charge with NH4(+) is nearly the same as that with Rb(+) and K(+), cations with similar GSFE and ionic radii. This indicates that proton transfer from NH4(+) to proteins plays an insignificant role in the extent of protein charging in native mass spectrometry.
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Affiliation(s)
| | | | - Evan R. Williams
- Address correspondence to Prof. Evan R. Williams: Department of Chemistry, University of California, Berkeley, B42 Hildebrand Hall Berkeley, CA 94720, Phone: (510) 643-7161,
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13
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Flick TG, Merenbloom SI, Williams ER. Effects of metal ion adduction on the gas-phase conformations of protein ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1654-62. [PMID: 23733259 PMCID: PMC3795793 DOI: 10.1007/s13361-013-0664-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/10/2013] [Accepted: 05/03/2013] [Indexed: 05/16/2023]
Abstract
Changes in protein ion conformation as a result of nonspecific adduction of metal ions to the protein during electrospray ionization (ESI) from aqueous solutions were investigated using traveling wave ion mobility spectrometry (TWIMS). For all proteins examined, protein cations (and in most cases anions) with nonspecific metal ion adducts are more compact than the fully protonated (or deprotonated) ions with the same charge state. Compaction of protein cations upon nonspecific metal ion binding is most significant for intermediate charge state ions, and there is a greater reduction in collisional cross section with increasing number of metal ion adducts and increasing ion valency, consistent with an electrostatic interaction between the ions and the protein. Protein cations with the greatest number of adducted metal ions are no more compact than the lowest protonated ions formed from aqueous solutions. These results show that smaller collisional cross sections for metal-attached protein ions are not a good indicator of a specific metal-protein interaction in solution because nonspecific metal ion adduction also results in smaller gaseous protein cation cross sections. In contrast, the collisional cross section of α-lactalbumin, which specifically binds one Ca(2+), is larger for the holo-form compared with the apo-form, in agreement with solution-phase measurements. Because compaction of protein cations occurs when metal ion adduction is nonspecific, elongation of a protein cation may be a more reliable indicator that a specific metal ion-protein interaction occurs in solution.
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Affiliation(s)
| | | | - Evan R. Williams
- Address reprint requests to Prof. Evan R. Williams: Department of Chemistry University of California, Berkeley Latimer Hall #1460 Berkeley, CA 94620-1460 Phone: (510) 643-7161 Fax: (510) 542-7714
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14
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Ma L, Wang Z, Liu S, Song F, Liu Z, Liu S. Screening calmodulin-binding ligands using intensity-fading matrix-assisted laser desorption/ionization mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:1527-1534. [PMID: 23722687 DOI: 10.1002/rcm.6594] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 04/07/2013] [Accepted: 04/07/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Calmodulin (CaM) plays an important role in the regulation of metabolism, cytoskeleton and cell proliferation. CaM antagonists are a class of drugs that can bind to CaM and modulate the interactions between CaM and their target biological processes. Screening new calmodulin antagonists and developing novel methods for detecting calmodulin ligands are important for developing novel anti-cancer drugs that bind specifically to CaM. METHODS An intensity-fading matrix-assisted laser desorption/ionization mass spectrometry (IF-MALDI-MS) method for screening calmodulin ligands was established, with the non-binding drug propranolol as the internal control. The experimental sample was prepared by mixing the positive ligand trifluoperazine (or chlorpromazine), propranolol and Ca(2+)-CaM. The control sample was treated in the same way without the addition of CaM. The experimental and control samples were both analyzed by MALDI-MS. Based on the relative intensity fading (IF) of the ligand to propranolol, the MS conditions were optimized and then used to study the binding of eight alkaloids and calmodulin. Competitive experiments were performed in a similar way by adding two drugs to compare their binding affinities with calmodulin. RESULTS The matrix 2,6-dihydroxyacetophenone (DHAP) was suitable for detecting calmodulin ligands. Compared with propranolol, the relative intensities of six free drugs (berbamine, tetrandrine, papaverine, reserpine, brucine and tetrahydropalmatine) clearly faded after the addition of calmodulin, indicating that they can bind with CaM. The other two alkaloids (strychnine and piperine) had no or weak interaction with the target protein. Based on the data from the competitive binding experiments, the binding affinities of five drugs to calmodulin were obtained in the order: tetrandrine > trifluoperazine > berbamine > chlorpromazine > imipramine. CONCLUSIONS The IF-MALDI-MS method was successfully applied to screen novel calmodulin agents at both qualitative and semiquantitative levels. The new ligands may be novel leads for CaM antagonists.
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Affiliation(s)
- Lei Ma
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun Center of Mass Spectrometry, Changchun, PR China
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15
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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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16
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Calcium-dependent conformational transition of calmodulin determined by Fourier transform infrared spectroscopy. Int J Biol Macromol 2013; 56:57-61. [PMID: 23403030 DOI: 10.1016/j.ijbiomac.2013.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 02/01/2013] [Accepted: 02/01/2013] [Indexed: 11/21/2022]
Abstract
The Ca(2+)-induced conformational changes in calmodulin (CaM) were monitored by Fourier transform infrared spectroscopy (FT-IR) at different molar ratios of Ca(2+) to CaM. The results show that these changes occur in two distinctive transitions. The first transition involves significant changes in the overall secondary structure with a small gain in solvent accessibility, and is completed after the second Ca(2+) binds to both EF-hands of its C-terminal domain. The second transition is accompanied by CaM folding into a tighter, less hydrogen-exchangeable structure, and is completed by the addition of the fourth Ca(2+) to have four Ca(2+) per molecule. Particularly, α-helices in CaM-nCa(2+)(n=0, 1, 2) are less stable than those in CaM-nCa(2+)(n=3, 4).
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Sperry JB, Ryan ZC, Kumar R, Gross ML. Hydrogen/Deuterium Exchange Reflects Binding of Human Centrin 2 to Ca(2+) and Xeroderma Pigmentosum Group C Peptide: An Example of EX1 Kinetics. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2012; 330-332:302-309. [PMID: 23439742 PMCID: PMC3578700 DOI: 10.1016/j.ijms.2012.10.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Xeroderma pigmentosum (XP) is a genetic disease affecting 1 in 10,000-100,000 and predisposes people to early-age skin cancer, a disease that is increasing. Those with XP have decreased ability to repair UV-induced DNA damage, leading to increased susceptibility of cancerous non-melanomas and melanomas. A vital, heterotrimeric protein complex is linked to the nucleotide excision repair pathway for the damaged DNA. The complex consists of XPC protein, human centrin 2, and RAD23B. One of the members, human centrin 2, is a ubiquitous, acidic, Ca(2+)-binding protein belonging to the calmodulin superfamily. The XPC protein contains a sequence motif specific for binding to human centrin 2. We report here the Ca(2+)-binding properties of human centrin 2 and its interaction with the XPC peptide motif. We utilized a region-specific H/D exchange protocol to localize the interaction of the XPC peptide with the C-terminal domain of centrin, the binding of which is different than that of calmodulin complexes. The binding dynamics of human centrin 2 to the XPC peptide in the absence and presence of Ca(2+) are revealed by the observation of EX1 H/D exchange regime, indicating that a locally unfolded population exists in solution and undergoes fast H/D exchange.
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Affiliation(s)
- Justin B Sperry
- Analytical Research and Development, Pfizer Inc., Chesterfield, MO 63017 ; Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
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18
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Brock A. Fragmentation hydrogen exchange mass spectrometry: A review of methodology and applications. Protein Expr Purif 2012; 84:19-37. [DOI: 10.1016/j.pep.2012.04.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/13/2012] [Indexed: 01/19/2023]
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19
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Wei H, Ahn J, Yu YQ, Tymiak A, Engen JR, Chen G. Using hydrogen/deuterium exchange mass spectrometry to study conformational changes in granulocyte colony stimulating factor upon PEGylation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:498-504. [PMID: 22227798 PMCID: PMC3438904 DOI: 10.1007/s13361-011-0310-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 11/22/2011] [Accepted: 11/28/2011] [Indexed: 05/12/2023]
Abstract
PEGylation is the covalent attachment of polyethylene glycol to proteins, and it can be used to alter immunogenicity, circulating half life and other properties of therapeutic proteins. To determine the impact of PEGylation on protein conformation, we applied hydrogen/deuterium exchange mass spectrometry (HDX MS) to analyze granulocyte colony stimulating factor (G-CSF) upon PEGylation as a model system. The combined use of HDX automation technology and data analysis software allowed reproducible and robust measurements of the deuterium incorporation levels for peptic peptides of both PEGylated and non-PEGylated G-CSF. The results indicated that significant differences in deuterium incorporation were induced by PEGylation of G-CSF, although the overall changes observed were quite small. PEGylation did not result in gross conformational rearrangement of G-CSF. The data complexity often encountered in HDX MS measurements was greatly reduced through a data processing and presentation format designed to facilitate the comparison process. This study demonstrates the practical utility of HDX MS for comparability studies, process monitoring, and protein therapeutic characterization in the biopharmaceutical industry.
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Affiliation(s)
- Hui Wei
- Department of Bioanalytical and Discovery Analytical Sciences, Bristol-Myers Squibb, Princeton, NJ, USA.
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20
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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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21
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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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22
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The effect of macromolecular crowding, ionic strength and calcium binding on calmodulin dynamics. PLoS Comput Biol 2011; 7:e1002114. [PMID: 21829336 PMCID: PMC3145654 DOI: 10.1371/journal.pcbi.1002114] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 05/23/2011] [Indexed: 11/20/2022] Open
Abstract
The flexibility in the structure of calmodulin (CaM) allows its binding to over 300 target proteins in the cell. To investigate the structure-function relationship of CaM, we combined methods of computer simulation and experiments based on circular dichroism (CD) to investigate the structural characteristics of CaM that influence its target recognition in crowded cell-like conditions. We developed a unique multiscale solution of charges computed from quantum chemistry, together with protein reconstruction, coarse-grained molecular simulations, and statistical physics, to represent the charge distribution in the transition from apoCaM to holoCaM upon calcium binding. Computationally, we found that increased levels of macromolecular crowding, in addition to calcium binding and ionic strength typical of that found inside cells, can impact the conformation, helicity and the EF hand orientation of CaM. Because EF hand orientation impacts the affinity of calcium binding and the specificity of CaM's target selection, our results may provide unique insight into understanding the promiscuous behavior of calmodulin in target selection inside cells. Proteins are workhorses for driving biological functions inside cells. Calmodulin (CaM) is a protein that can carry cellular signals by triggered conformational changes due to calcium binding that alters target binding. Interestingly, CaM is able to bind over 300 targets. One of the challenges in characterizing CaM's ability to bind multiple targets lies in that CaM is a flexible protein and its structure is easily modulated by the physicochemical changes in its surroundings, particularly inside a complex cellular milieu. In order to determine structure-function relationships of CaM, we employed a combined approach of experiments, computer simulations and statistical physics in the investigation of the effect of calcium-binding, salt concentration, and macromolecular crowding on CaM. The results revealed unique folding energy landscapes of CaM in the absence and presence of calcium ions and the structural implications of CaM are interpreted under cell-like conditions. Further, a large conformational change in CaM in response to environmental impacts, dictates the packing of local helices that may be critical to its function of target binding and recognition among vast target selections.
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23
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Huang RYC, Rempel DL, Gross ML. HD exchange and PLIMSTEX determine the affinities and order of binding of Ca2+ with troponin C. Biochemistry 2011; 50:5426-35. [PMID: 21574565 PMCID: PMC3115450 DOI: 10.1021/bi200377c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Troponin C (TnC), present in all striated muscle, is the Ca(2+)-activated trigger that initiates myocyte contraction. The binding of Ca(2+) to TnC initiates a cascade of conformational changes involving the constituent proteins of the thin filament. The functional properties of TnC and its ability to bind Ca(2+) have significant regulatory influence on the contractile reaction of muscle. Changes in TnC may also correlate with cardiac and various other muscle-related diseases. We report here the implementation of the PLIMSTEX strategy (protein ligand interaction by mass spectrometry, titration, and H/D exchange) to elucidate the binding affinity of TnC with Ca(2+) and, more importantly, to determine the order of Ca(2+) binding of the four EF hands of the protein. The four equilibrium constants, K(1) = (5 ± 5) × 10(7) M(-1), K(2) = (1.8 ± 0.8) × 10(7) M(-1), K(3) = (4.2 ± 0.9) × 10(6) M(-1), and K(4) = (1.6 ± 0.6) × 10(6) M(-1), agree well with determinations by other methods and serve to increase our confidence in the PLIMSTEX approach. We determined the order of binding to the four EF hands to be III, IV, II, and I by extracting from the H/DX results the deuterium patterns for each EF hand for each state of the protein (apo through fully Ca(2+) bound). This approach, demonstrated for the first time, may be general for determining binding orders of metal ions and other ligands to proteins.
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Affiliation(s)
- Richard Y-C. Huang
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Don L. Rempel
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
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Sperry JB, Huang RYC, Zhu MM, Rempel DL, Gross ML. Hydrophobic Peptides Affect Binding of Calmodulin and Ca as Explored by H/D Amide Exchange and Mass Spectrometry. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2011; 302:85-92. [PMID: 21765646 PMCID: PMC3134286 DOI: 10.1016/j.ijms.2010.08.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Calmodulin (CaM), a ubiquitous intracellular sensor protein, binds Ca(2+) and interacts with various targets as part of signal transduction. Using hydrogen/deuterium exchange (H/DX) and a high resolution PLIMSTEX (Protein-Ligand Interactions by Mass Spectrometry, Titration, and H/D Exchange) protocol, we examined five different states of calmodulin: calcium-free, calcium-loaded, and three states of calcium-loaded in the presence of either melittin, mastoparan, or skeletal myosin light-chain kinase (MLCK). When CaM binds Ca(2+), the extent of HDX decreased, consistent with the protein becoming stabilized upon binding. Furthermore, Ca(2+)-saturated calmodulin exhibits increased protection when bound to the peptides, forming high affinity complexes. The protocol reveals significant changes in EF hands 1, 3, and 4 with saturating levels of Ca(2+). Titration of the protein using PLIMSTEX provides the binding affinity of Ca(2+) to calmodulin within previously reported values. The affinities of calmodulin to Ca(2+) increase by factors of 300 and 1000 in the presence of melittin and mastoparan, respectively. A modified PLIMSTEX protocol whereby the protein is digested to component peptides gives a region-specific titration. The titration data taken in this way show a decrease in the root mean square fit of the residuals, indicating a better fit of the data. The global H/D exchange results and those obtained in a region-specific way provide new insight into the Ca(2+)-binding properties of this well-studied protein.
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Affiliation(s)
- Justin B Sperry
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, POBox 1134, St. Louis, MO 63130
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25
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Ramisetty SR, Washburn MP. Unraveling the dynamics of protein interactions with quantitative mass spectrometry. Crit Rev Biochem Mol Biol 2011; 46:216-28. [PMID: 21438726 DOI: 10.3109/10409238.2011.567244] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Knowledge of structure and dynamics of proteins and protein complexes is important to unveil the molecular basis and mechanisms involved in most biological processes. Protein complex dynamics can be defined as the changes in the composition of a protein complex during a cellular process. Protein dynamics can be defined as conformational changes in a protein during enzyme activation, for example, when a protein binds to a ligand or when a protein binds to another protein. Mass spectrometry (MS) combined with affinity purification has become the analytical tool of choice for mapping protein-protein interaction networks and the recent developments in the quantitative proteomics field has made it possible to identify dynamically interacting proteins. Furthermore, hydrogen/deuterium exchange MS is emerging as a powerful technique to study structure and conformational dynamics of proteins or protein assemblies in solution. Methods have been developed and applied for the identification of transient and/or weak dynamic interaction partners and for the analysis of conformational dynamics of proteins or protein complexes. This review is an overview of existing and recent developments in studying the overall dynamics of in vivo protein interaction networks and protein complexes using MS-based methods.
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26
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Zhang H, Gau BC, Jones LM, Vidavsky I, Gross ML. Fast photochemical oxidation of proteins for comparing structures of protein-ligand complexes: the calmodulin-peptide model system. Anal Chem 2011; 83:311-8. [PMID: 21142124 PMCID: PMC3078576 DOI: 10.1021/ac102426d] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Fast photochemical oxidation of proteins (FPOP) is a mass spectrometry-based protein footprinting method that modifies proteins on the microsecond time scale. Highly reactive (•)OH, produced by laser photolysis of hydrogen peroxide, oxidatively modifies the side chains of approximately one-half the common amino acids on this time scale. Because of the short labeling exposure, only solvent-accessible residues are sampled. Quantification of the modification extent for the apo and holo states of a protein-ligand complex provides structurally sensitive information at the amino-acid level to compare the structures of unknown protein complexes with known ones. We report here the use of FPOP to monitor the structural changes of calmodulin in its established binding to M13 of the skeletal muscle myosin light chain kinase. We use the outcome to establish the unknown structures resulting from binding with melittin and mastoparan. The structural comparison follows a comprehensive examination of the extent of FPOP modifications as measured by proteolysis and LC-MS/MS for each protein-ligand equilibrium. The results not only show that the three calmodulin-peptide complexes have similar structures but also reveal those regions of the protein that became more or less solvent-accessible upon binding. This approach has the potential for relatively high throughput, information-dense characterization of a series of protein-ligand complexes in biochemistry and drug discovery when the structure of one reference complex is known, as is the case for calmodulin and M13 of the skeletal muscle myosin light chain kinase, and the structures of related complexes are not.
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Affiliation(s)
- Hao Zhang
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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27
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Su D, Delaplane S, Luo M, Rempel DL, Vu B, Kelley MR, Gross ML, Georgiadis MM. Interactions of apurinic/apyrimidinic endonuclease with a redox inhibitor: evidence for an alternate conformation of the enzyme. Biochemistry 2010; 50:82-92. [PMID: 21117647 DOI: 10.1021/bi101248s] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Apurinic/apyrimidinic endonuclease (APE1) is an essential base excision repair protein that also functions as a reduction and oxidation (redox) factor in mammals. Through a thiol-based mechanism, APE1 reduces a number of important transcription factors, including AP-1, p53, NF-κB, and HIF-1α. What is known about the mechanism to date is that the buried residues Cys 65 and Cys 93 are critical for APE1's redox activity. To further detail the redox mechanism, we developed a chemical footprinting-mass spectrometric assay using N-ethylmaleimide (NEM), an irreversible Cys modifier, to characterize the interaction of the redox inhibitor, E3330, with APE1. When APE1 was incubated with E3330, two NEM-modified products were observed, one with two and a second with seven added NEMs; this latter product corresponds to a fully modified APE1. In a similar control reaction without E3330, only the +2NEM product was observed in which the two solvent-accessible Cys residues, C99 and C138, were modified by NEM. Through hydrogen-deuterium amide exchange with analysis by mass spectrometry, we found that the +7NEM-modified species incorporates approximately 40 more deuterium atoms than the native protein, which exchanges nearly identically as the +2NEM product, suggesting that APE1 can be trapped in a partially unfolded state. E3330 was also found to increase the extent of disulfide bond formation involving redox critical Cys residues in APE1 as assessed by liquid chromatography and tandem mass spectrometry, suggesting a basis for its inhibitory effects on APE1's redox activity. Collectively, our results suggest that APE1 adopts a partially unfolded state, which we propose is the redox active form of the enzyme.
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Affiliation(s)
- Dian Su
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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28
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Ciampa EJ, Welch RC, Vanoye CG, George AL. KCNE4 juxtamembrane region is required for interaction with calmodulin and for functional suppression of KCNQ1. J Biol Chem 2010; 286:4141-9. [PMID: 21118809 DOI: 10.1074/jbc.m110.158865] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated potassium (K(V)) channels, such as KCNQ1 (K(V)7.1), are modulated by accessory subunits and regulated by intracellular second messengers. Accessory subunits belonging to the KCNE family exert diverse functional effects on KCNQ1, have been implicated in the pathogenesis of various genetic disorders of heart rhythm, and contribute to transducing intracellular signaling events into changes in K(V) channel activity. We investigated the interactions between calmodulin (CaM), the ubiquitous Ca(2+)-transducing protein that binds and confers Ca(2+) sensitivity to the biophysical properties of KCNQ1, and KCNE4. These studies were motivated by the observed similarities between the suppression of KCNQ1 function by pharmacological disruption of KCNQ1-CaM interactions and the effects of KCNE4 co-expression on the channel. We determined that KCNE4, but not KCNE1, can biochemically interact with CaM and that this interaction is Ca(2+)-dependent and requires a tetraleucine motif in the juxtamembrane region of the KCNE4 C terminus. Furthermore, disruption of the KCNE4-CaM interaction either by mutagenesis of the tetraleucine motif or by acute Ca(2+) chelation impairs the ability of KCNE4 to inhibit KCNQ1. Our findings have potential relevance to KCNQ1 regulation both by KCNE accessory subunits and by an important intracellular signaling molecule.
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Affiliation(s)
- Erin J Ciampa
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, USA
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29
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Tu T, Drăguşanu M, Petre BA, Rempel DL, Przybylski M, Gross ML. Protein-peptide affinity determination using an h/d exchange dilution strategy: application to antigen-antibody interactions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1660-1667. [PMID: 20444623 PMCID: PMC2932787 DOI: 10.1016/j.jasms.2010.03.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 05/27/2023]
Abstract
A new methodology using hydrogen/deuterium amide exchange (HDX) to determine the binding affinity of protein-peptide interactions is reported. The method, based on our previously established approach, protein ligand interaction by mass spectrometry, titration, and H/D exchange (PLIMSTEX) [J. Am. Chem. Soc.2003, 125, 5252-5253], makes use of a dilution strategy (dPLIMSTEX) for HDX, using the mass of the peptide ligand as readout. We employed dPLIMSTEX to study the interaction of calcium-saturated calmodulin with the opioid peptide β-endorphin as a model system; the affinity results are in good agreement with those from traditional PLIMSTEX and with literature values obtained by using other methods. We show that the dPLIMSTEX method is feasible to quantify an antigen-antibody interaction involving a 3-nitrotyrosine modified peptide in complex with a monoclonal anti-nitrotyrosine antibody. A dissociation constant in the low nanomolar range was determined, and a binding stoichiometry of antibody/peptide of 1:2 was confirmed. In addition, we determined that the epitope in the binding interface contains a minimum of five amino acids. The dPLIMSTEX approach is a sensitive and powerful tool for the quantitative determination of peptide affinities with antibodies, complementary to conventional immuno-analytical techniques.
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Affiliation(s)
- Tingting Tu
- Center for Biomedical and Bioorganic Mass Spectrometry, Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Mihaela Drăguşanu
- Laboratory of Analytical Chemistry and Biopolymer Structure Analysis, Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Brînduşa-Alina Petre
- Laboratory of Analytical Chemistry and Biopolymer Structure Analysis, Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Don L. Rempel
- Center for Biomedical and Bioorganic Mass Spectrometry, Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Michael Przybylski
- Laboratory of Analytical Chemistry and Biopolymer Structure Analysis, Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Michael L. Gross
- Center for Biomedical and Bioorganic Mass Spectrometry, Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
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30
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Pan J, Konermann L. Calcium-Induced Structural Transitions of the Calmodulin−Melittin System Studied by Electrospray Mass Spectrometry: Conformational Subpopulations and Metal-Unsaturated Intermediates. Biochemistry 2010; 49:3477-86. [DOI: 10.1021/bi100261c] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Jingxi Pan
- 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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31
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Wyttenbach T, Grabenauer M, Thalassinos K, Scrivens JH, Bowers MT. The effect of calcium ions and peptide ligands on the relative stabilities of the calmodulin dumbbell and compact structures. J Phys Chem B 2010; 114:437-47. [PMID: 20000583 DOI: 10.1021/jp906242m] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A combination of ion mobility and mass spectrometry methods was used to characterize the molecular shape of the protein calmodulin (CaM) and its complexes with calcium and a number of peptide ligands. CaM, a calcium-binding protein composed of 148 amino acid residues, was found by X-ray crystallography to occur both in a globular shape and in the shape of an extended dumbbell. Here, it was found, as solutions of CaM and CaM complexes were sprayed into the solvent-free environment of the mass spectrometer, that major structural features of the molecule and the stoichiometry of the units constituting a complex in solution were preserved in the desolvation process. Two types of CaM structures were observed in our experiments: a compact and an extended form of CaM with measured cross sections in near-perfect agreement with those calculated for the known globular and extended dumbbell X-ray geometries. Calcium-free solutions yielded predominantly an extended CaM conformation. Ca(n)(2+)-CaM complexes were observed in calcium-containing solutions, n = 0-4, with the population of the compact conformation increasing relative to the elongated conformation as n increases. For n = 4, a predominantly compact globular conformation was observed. Solutions containing the peptide CaMKII(290-309), the CaM target domain of the Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) enzyme, yielded predominantly globular Ca(4)(2+)-CaM-CaMKII(290-309) complexes. Similar results were obtained with the 26-residue peptide melittin. For the 14-residue C-terminal melittin fragment, on the other hand, formation of both a 1:1 and a 1:2 CaM-peptide complex was detected. On the basis of the entirety of our results, we conclude that the collapse of extended (dumbbell-like) CaM structures into more compact globular structures occurs upon specific binding of four calcium ions. Furthermore, this calcium-induced structural collapse of CaM appears to be a prerequisite for formation of a particularly stable CaM-peptide complex involving peptides long enough to be engaged in interactions with both lobes of CaM.
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Affiliation(s)
- Thomas Wyttenbach
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, USA
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32
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Kaltashov IA, Bobst CE, Abzalimov RR. H/D exchange and mass spectrometry in the studies of protein conformation and dynamics: is there a need for a top-down approach? Anal Chem 2009; 81:7892-9. [PMID: 19694441 PMCID: PMC2805115 DOI: 10.1021/ac901366n] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hydrogen/deuterium exchange (HDX) combined with mass spectrometry (MS) detection has matured in recent years to become a powerful tool in structural biology and biophysics. Several limitations of this technique can and will be addressed by tapping into the ever expanding arsenal of methods to manipulate ions in the gas phase offered by mass spectrometry.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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Percy AJ, Slysz GW, Schriemer DC. Surrogate H/D Detection Strategy for Protein Conformational Analysis Using MS/MS Data. Anal Chem 2009; 81:7900-7. [DOI: 10.1021/ac901148u] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Andrew J. Percy
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Gordon W. Slysz
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - David C. Schriemer
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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Shirran SL, Barran PE. The use of ESI-MS to probe the binding of divalent cations to calmodulin. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1159-1171. [PMID: 19297189 DOI: 10.1016/j.jasms.2009.02.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 02/05/2009] [Accepted: 02/05/2009] [Indexed: 05/27/2023]
Abstract
Proteins have evolved with distinct sites for binding particular metal ions. This allows metalloproteins to perform a myriad of specialized tasks with conformations tailor-made by the combination of its primary sequence and the effect on this of the ligated metal ion. Here we investigate the selectivity of the calcium trigger protein calmodulin for divalent metal ions. This ubiquitous and highly abundant protein exists in equilibrium between its apo and its holo form wherein four calcium ions are bound. Amongst its many functions, calmodulin modulates the calcium concentration present in cells, but this functional property renders it a target for competition from other metal ions. We study the competition posed by four other divalent cations for the calcium binding sites in calmodulin using electrospray ionization mass spectrometry (ESI-MS). We have chosen two other group II cations Mg(2+), Sr(2+), and two heavy metals Cd(2+), Pb(2+). The ease with which each of these metals binds to apo and to holo CaM[4Ca] is described. We find that each metal ion has different properties with respect to calmodulin binding and competition with calcium. The order of affinity for apo CaM is Ca(2+) >> Sr(2+) approximately Mg(2+) > Pb(2+) approximately Cd(2+). In the presence of calcium the affinity alters to Pb(2+) > Ca(2+) > Cd(2+) > Sr(2+) > Mg(2+). Once complexes have been formed between the metal ions and protein (CaM:[xM]) we investigate whether the structural change which must accompanies calcium ligation to allow target binding takes place for a given CaM:[xM] system. We use a 20 residue target peptide, which forms the CaM binding site within the enzyme neuronal nitric-oxide synthase. Our earlier work (Shirran et al. 2005) [1] has demonstrated the particular selectivity of this system for CaM:4Ca(2+). We find that along with Ca(2+) only Pb(2+) forms complexes of the form CaM:4M(2+):nNOS. This work demonstrates the affinity for calcium above all other metals, but also warns about the ability of lead to replace calcium with apparent ease.
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Affiliation(s)
- Sally L Shirran
- School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
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35
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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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Wang Z, Yu X, Cui M, Liu Z, Song F, Liu S. Investigation of calmodulin-Peptide interactions using matrix-assisted laser desorption/ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:576-583. [PMID: 19110443 DOI: 10.1016/j.jasms.2008.11.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2008] [Revised: 11/20/2008] [Accepted: 11/20/2008] [Indexed: 05/27/2023]
Abstract
In this report, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was used to study the binding interactions between calmodulin and two target peptides (melittin and substance P). Various matrix conditions were tested and the less acidic matrix DHAP and THAP were found to favor the survival of the intact calcium-calmodulin as well as the calmodulin-peptide complexes. However, the application of direct MALDI-MS to detect the intact complexes turned out to be very difficult due to the dissociation of the complexes and the formation of nonspecific aggregates. In contrast, the specific binding of the target peptides to calmodulin could be easily deduced using intensity-fading (IF) MALDI-MS. Compared with the nonbinding control, clear reduction in the ion abundances of the target peptides was observed with the addition of calmodulin. Relative binding affinities of different peptides towards the protein could also be estimated using IF-MALDI-MS. This study may extend the application of IF-MALDI-MS in the analysis of noncovalent complexes and offer a perspective into the utility of MALDI-MS as an alternative approach to study the peptides binding to calmodulin.
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Affiliation(s)
- Zhaofu Wang
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun Center of Mass Spectrometry, Changchun, PR China
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Ly T, Julian RR. Protein-metal interactions of calmodulin and alpha-synuclein monitored by selective noncovalent adduct protein probing mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:1663-1672. [PMID: 18691903 DOI: 10.1016/j.jasms.2008.07.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 07/08/2008] [Accepted: 07/08/2008] [Indexed: 05/26/2023]
Abstract
The metal binding properties of proteins are biologically significant, particularly in relationship to the molecular origins of disease and the discovery of therapeutic pharmaceutical treatments. Herein, we demonstrate that selective noncovalent adduct protein probing mass spectrometry (SNAPP-MS) is a sensitive technique to investigate the structural effects of protein-metal interactions. We utilize specific, noncovalent interactions between 18-crown-6 ether (18C6) and lysine to probe protein structure in the presence and absence of metal ions. Application of SNAPP-MS to the calmodulin-Ca2+ system demonstrates that changes in protein structure are reflected in a substantial change in the number and intensity of 18C6s, which bind to the protein as observed by MS. In this manner, SNAPP is demonstrated to be a sensitive technique for monitoring ligand-induced conformational rearrangements in proteins. In addition, SNAPP is well-suited to examine the properties of natively unfolded proteins, where structural changes are more difficult to detect by other methods. For example, alpha-synuclein is a protein associated in the pathology of Parkinson's disease, which is known to aggregate more rapidly in the presence of Al3+ and Cu2+. The 18C6 SNAPP distributions for alpha-synuclein change dramatically in the presence of 3 microM Al3+, revealing that Al3+ binding causes a significant change in the conformational dynamics of the monomeric form of this disordered protein. In contrast, binding of Cu2+ does not induce a significant shift in 18C6 binding, suggesting that noteworthy structural reorganizations at the monomeric level are minimal. These results are consistent with the idea that the metal-induced aggregation caused by Al3+ and Cu2+ proceed by independent pathways.
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Affiliation(s)
- Tony Ly
- Department of Chemistry, University of California-Riverside, Riverside, California 92521, USA
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38
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Pukala TL, Urathamakul T, Watt SJ, Beck JL, Jackway RJ, Bowie JH. Binding studies of nNOS-active amphibian peptides and Ca2+ calmodulin, using negative ion electrospray ionisation mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:3501-3509. [PMID: 18853393 DOI: 10.1002/rcm.3757] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Amphibian peptides which inhibit the formation of nitric oxide by neuronal nitric oxide synthase (nNOS) do so by binding to the protein cofactor, Ca2+calmodulin (Ca2+CaM). Complex formation between active peptides and Ca2+CaM has been demonstrated by negative ion electrospray ionisation mass spectrometry using an aqueous ammonium acetate buffer system. In all cases studied, the assemblies are formed with a 1:1:4 calmodulin/peptide/Ca2+ stoichiometry. In contrast, the complex involving the 20-residue binding domain of the plasma Ca2+ pump C20W (LRRGQILWFRGLNRIQTQIK-OH) with CaM has been shown by previous two-dimensional nuclear magnetic resonance (2D NMR) studies to involve complexation of the C-terminal end of CaM. Under identical conditions to those used for the amphibian peptide study, the ESI complex between C20W and CaM shows specific 1:1:2 stoichiometry. Since complex formation with the studied amphibian peptides requires Ca2+CaM to contain its full complement of four Ca2+ ions, this indicates that the amphibian peptides require both ends of the CaM to effect complex formation. Charge-state analysis and an H/D exchange experiment (with caerin 1.8) suggest that complexation involves Ca2+CaM undergoing a conformational change to a more compact structure.
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Affiliation(s)
- Tara L Pukala
- Department of Chemistry, The University of Adelaide, South Australia, 5005, Australia
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Slysz GW, Percy AJ, Schriemer DC. Restraining Expansion of the Peak Envelope in H/D Exchange-MS and Its Application in Detecting Perturbations of Protein Structure/Dynamics. Anal Chem 2008; 80:7004-11. [DOI: 10.1021/ac800897q] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gordon W. Slysz
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Andrew J. Percy
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - David C. Schriemer
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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Wang Q, Li S, Li C, Liang J, Fang Z, Xie L, Zhang R. The extra C-terminal tail is involved in the conformation, stability changes and the N/C-domain interactions of the calmodulin-like protein from pearl oyster Pinctada fucata. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1514-23. [PMID: 18675945 DOI: 10.1016/j.bbapap.2008.06.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2007] [Revised: 06/08/2008] [Accepted: 06/23/2008] [Indexed: 11/18/2022]
Abstract
Pearl oyster Pinctada fucata calmodulin-like protein (PfCaLP), containing an extra tail (D150-K161) at the C-terminal, is a novel protein involved in the regulation of oyster calcium metabolism. The purpose of this study is to gain insight into the conformational characteristics of the N/C-domain of PfCaLP, especially the detailed contribution of the extra tail to the Ca(2+)/Mg(2+)-induced conformational changes, the stability of the intact PfCaLP molecule and its C-domain, as well as to the interdomain communications in PfCaLP. Our results demonstrate that a strong interaction exists between the hydrophilic tail and the C-domain of PfCaLP. The extra tail, through affecting the C-domain conformational changes, further influences the migration rate, conformational changes, N/C-domain interactions and exposure of the hydrophobic patches of the intact PfCaLP molecule. Furthermore, the tail could actively regulate the stability of PfCaLP and its C-domain. Our studies are helpful to explain our previous finding that the tail plays important roles in PfCaLP-target interaction in the oyster calcium metabolism.
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Affiliation(s)
- Qin Wang
- Institute of Marine Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China
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41
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Li Y, Williams TD, Schowen RL, Topp EM. Trehalose and calcium exert site-specific effects on calmodulin conformation in amorphous solids. Biotechnol Bioeng 2007; 97:1650-3. [PMID: 17286268 DOI: 10.1002/bit.21362] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have adapted hydrogen/deuterium (H/D) exchange with electrospray ionization mass spectrometry (ESI-MS) to study protein conformation and excipient interactions in lyophilized solids. Using calmodulin (CaM, 17 kD) as a model protein, we demonstrate that trehalose and calcium exert site-specific effects on protein conformation. The effects of calcium are observed primarily in the calcium binding loops, while those of trehalose are observed primarily in non-terminal alpha-helical regions. To our knowledge, this is the first demonstration of site-specificity in the effects of excipients on protein structure in the solid state, and of the utility of H/D exchange with ESI-MS to characterize proteins in amorphous solids.
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Affiliation(s)
- Yunsong Li
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, USA
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42
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Li Y, Williams TD, Schowen RL, Topp EM. Characterizing protein structure in amorphous solids using hydrogen/deuterium exchange with mass spectrometry. Anal Biochem 2007; 366:18-28. [PMID: 17490599 DOI: 10.1016/j.ab.2007.03.041] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2006] [Revised: 03/28/2007] [Accepted: 03/29/2007] [Indexed: 10/23/2022]
Abstract
Elucidating protein structure in amorphous solids is central to the rational design of stable lyophilized protein drugs. Hydrogen/deuterium (H/D) exchange with electrospray ionization mass spectrometry was applied to lyophilized powders containing calmodulin (17 kDa) and exposed to D(2)O vapor at controlled relative humidity (RH) and temperature. H/D exchange was influenced by RH and by the inclusion of calcium chloride and/or trehalose in the solid. The effects were not exhibited uniformly along the protein backbone but occurred in a site-specific manner, with calcium primarily influencing the calcium-binding loops and trehalose primarily influencing the alpha-helices. The results demonstrate that the method can provide quantitative and site-specific structural information on proteins in amorphous solids and on changes in structure induced by protein cofactors and formulation excipients. Such information is not readily available with other techniques used to characterize proteins in the solid state, such as Fourier transform infrared, Raman, and near-infrared spectroscopy.
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Affiliation(s)
- Yunsong Li
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, USA
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43
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Li Y, Williams TD, Topp EM. Effects of Excipients on Protein Conformation in Lyophilized Solids by Hydrogen/Deuterium Exchange Mass Spectrometry. Pharm Res 2007; 25:259-67. [PMID: 17597380 DOI: 10.1007/s11095-007-9365-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Accepted: 05/30/2007] [Indexed: 10/23/2022]
Abstract
PURPOSE Excipients are added to lyophilized protein drug formulations to protect the protein during processing and storage, but the mechanisms are poorly understood. Here, hydrogen/deuterium (H/D) exchange with mass spectrometry was used to assess protein conformation and excipient interactions in lyophilized solids. METHODS Calmodulin (CaM, 17 kD) was co-lyophilized with carbohydrate excipients (sucrose, mannitol, trehalose, raffinose, dextran 5,000, dextran 12,000) or guanidine hydrochloride (negative control) and exposed to D2O vapor at 33% RH and RT. Samples were then dissolved and analyzed by mass spectrometry (+ESI/MS). Peptic digestion provided additional, site-specific information on H/D exchange. Solids were further characterized by powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and water vapor sorption. RESULTS Excipients protected CaM from H/D exchange, increasing in the order guanidine hydrochloride < no excipient, mannitol < dextran 5,000, dextran 12,000 < sucrose < raffinose < trehalose. Effects were exerted primarily in the protein's alpha-helical segments. CONCLUSIONS The effects of carbohydrate excipients on protein conformation in lyophilized solids are not exhibited uniformly along the protein sequence, but instead are exerted in a site-specific manner. The results also demonstrate the utility of H/D exchange with ESI/MS for protein structure characterization in lyophilized samples.
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Affiliation(s)
- Yunsong Li
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS, 66047, USA
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44
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Seyfried NT, Atwood JA, Yongye A, Almond A, Day AJ, Orlando R, Woods RJ. Fourier transform mass spectrometry to monitor hyaluronan-protein interactions: use of hydrogen/deuterium amide exchange. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:121-31. [PMID: 17154353 PMCID: PMC4189122 DOI: 10.1002/rcm.2817] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The use of Fourier transform mass spectrometry (FTMS) to monitor noncovalent complex formation in the gas phase under native conditions between the Link module from human tumor necrosis factor stimulated gene-6 (Link_TSG6) and hyaluronan (HA) oligosaccharides is reported. In particular, a titration experiment with increasing concentrations of octasaccharide (HA(8)) to protein produced a noncovalent complex with 1:1 stoichiometry when the oligosaccharide was in molar excess. However, in the presence of a molar excess of tetrasaccharide (HA(4)) nearly all proteins and oligosaccharides were observed in their unbound charge states. These results are consistent with solution-phase properties for this interaction in which HA(8), but not HA(4), supports high affinity Link_TSG6 binding. Hydrogen/deuterium amide exchange mass spectrometry (H/D-EX MS) was also utilized to investigate the level of global deuterium incorporation, over time, for Link_TSG6 in both the absence and presence of HA(8). After dilution into quenching conditions, deuterium incorporation reached limiting asymptotic values of 37 and 26 deuterons for the free and bound protein at 240 and 480 min, respectively, indicating that the oligosaccharide interferes with amide exchange on binding. To detect sequence-specific deuterium incorporation, pepsin digestion of Link_TSG6 in both the absence and presence of HA(8) was performed. A level of deuterium incorporation of 10-30% was observed for peptides analyzed in free Link_TSG6. Interestingly, HA(8) blocked some sites of proteolysis in Link_TSG6 compared to the free protein. Molecular modeling indicated that amino acids proximal to the ligand correlated with regions of the protein that were resistant to enzymatic digestion. Of the peptides that could be analyzed by H/D-EX MS in the presence of the ligand, a 30-60% reduction in deuterium incorporation, relative to the free protein, was observed, even for those sequences not directly involved in HA binding. These results support the utility of FTMS as a method for the characterization of protein-carbohydrate interactions.
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Affiliation(s)
- Nicholas T. Seyfried
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - James A. Atwood
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Austin Yongye
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Andrew Almond
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Anthony J. Day
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | - Ron Orlando
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Robert J. Woods
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
- Correspondence to: R. J. Woods, Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA.
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Chitta RK, Rempel DL, Grayson MA, Remsen EE, Gross ML. Application of SIMSTEX to oligomerization of insulin analogs and mutants. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1526-1534. [PMID: 16952461 DOI: 10.1016/j.jasms.2006.08.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Revised: 08/04/2006] [Accepted: 08/04/2006] [Indexed: 05/11/2023]
Abstract
The propensity of various insulins and their analogs to oligomerize was investigated by mass spectrometric methods including measurement of the relative abundances of oligomers in the gas phase and the kinetics of H/D amide exchange. The kinetics of deuterium uptake show a good fit when the exchanging amides are placed in three kinetic groups: fast, intermediate, and slow. r-Human insulin, of the insulins investigated, has fewer amides that exchange at intermediate rates and more that exchange at slow rates, in accord with its higher extent of association in solution. We adapted PLIMSTEX (protein ligand interactions by mass spectrometry, titration, and H/D exchange) to determine protein/ligand affinities in solution, to determine self-association equilibrium constants for proteins, and to apply them to various insulin analogs. We term this adaptation SIMSTEX (self-association interactions using mass spectrometry, self-titration and H/D exchange); it gives affinity constants that compare well with the literature results. The results from SIMSTEX show that some mutants (e.g., GlnB13) have an increased tendency to self-associate, possibly slowing down their action in vivo. Other mutants (e.g., lispro and AspB9) have lower propensities for self-association, thus providing potentially faster-acting analogs for use in controlling diabetes.
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Affiliation(s)
- Raghu K Chitta
- Department of Chemistry, Washington University, One Brookings Drive, Box 1134, 63130, St. Louis, MO, USA
| | - Don L Rempel
- Department of Chemistry, Washington University, One Brookings Drive, Box 1134, 63130, St. Louis, MO, USA
| | - Michael A Grayson
- Department of Chemistry, Washington University, One Brookings Drive, Box 1134, 63130, St. Louis, MO, USA
| | - Edward E Remsen
- Department of Chemistry, Washington University, One Brookings Drive, Box 1134, 63130, St. Louis, MO, USA
| | - Michael L Gross
- Department of Chemistry, Washington University, One Brookings Drive, Box 1134, 63130, St. Louis, MO, USA.
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46
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Wakankar AA, Borchardt RT. Formulation considerations for proteins susceptible to asparagine deamidation and aspartate isomerization. J Pharm Sci 2006; 95:2321-36. [PMID: 16960822 DOI: 10.1002/jps.20740] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The asparagine (Asn) deamidation and aspartate (Asp) isomerization reactions are nonenzymatic intra-molecular reactions occurring in peptides and proteins that are a source of major stability concern in the formulation of these biomolecules. The mechanisms for the deamidation and isomerization reactions are similar since they both proceed through an intra-molecular cyclic imide (Asu) intermediate. The formation of the Asu intermediate, which involves the attack by nitrogen of the peptide backbone on the carbonyl carbon of the Asn or the Asp side chain, is the rate-limiting step in both the deamidation and the isomerization reactions at physiological pH. In this article, the influence of factors such as formulation conditions, protein primary sequence, and protein structure on the reactivity of Asn and Asp residues in proteins are reviewed. The importance of formulation conditions such as pH and solvent dielectric in influencing deamidation and isomerization reaction rates is addressed. Formulation strategies that could improve the stability of proteins to deamidation and isomerization reactions are described. The review is intended to provide information to formulation scientists, based on protein sequence and structure, to predict potential degradative sites on a protein molecule and to enable formulation scientists to set appropriate formulation conditions to minimize reactivity of Asn and Asp residues in protein therapeutics.
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Affiliation(s)
- Aditya A Wakankar
- Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, Kansas 66047, USA.
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47
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Kaltashov IA, Zhang M, Eyles SJ, Abzalimov RR. Investigation of structure, dynamics and function of metalloproteins with electrospray ionization mass spectrometry. Anal Bioanal Chem 2006; 386:472-81. [PMID: 16932945 DOI: 10.1007/s00216-006-0636-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 06/06/2006] [Accepted: 06/19/2006] [Indexed: 10/24/2022]
Abstract
Electrospray ionization mass spectrometry (ESI MS) has emerged recently as a powerful tool for analyzing many structural and behavioral aspects of metalloproteins in great detail. In this review we discuss recent developments in the field, placing particular emphasis on the unique features of ESI MS that lend themselves to metalloprotein characterization at a variety of levels. Direct mass measurement enables the determination of protein-metal ion binding stoichiometry in solution and metalloprotein higher order structure in the case of multi-subunit proteins. MS techniques have been developed for determining the locations of metal-binding centers, metal oxidation states and reaction intermediates of metal-containing enzymes. Other ESI MS techniques are also discussed, such as protein ion charge state distributions and hydrogen/deuterium exchange studies, which can be used to measure metal binding affinities and to shed light on vital dynamic aspects of the functional properties of metalloproteins endowed by metal binding.
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Affiliation(s)
- Igor A Kaltashov
- Department of Chemistry, University of Massachusetts-Amherst, 710 North Pleasant Street, Amherst, MA 01003, USA.
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48
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Li S, Xie L, Meng Q, Zhang R. Significance of the extra C-terminal tail of CaLP, a novel calmodulin-like protein involved in oyster calcium metabolism. Comp Biochem Physiol B Biochem Mol Biol 2006; 144:463-71. [PMID: 16759893 DOI: 10.1016/j.cbpb.2006.04.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2006] [Revised: 04/14/2006] [Accepted: 04/22/2006] [Indexed: 11/22/2022]
Abstract
Oyster (Pinctada fucata) calmodulin-like protein (CaLP), containing a C-terminally extra hydrophilic tail (150D-161K), is a novel protein involved in the regulation of oyster calcium metabolism. To investigate the importance of the extra fragment to the Ca(2+)/Mg(2+)-dependent conformational changes in the intact CaLP molecule and the interactions between CaLP and its target proteins, a truncated CaLP mutant (M-CaLP) devoid of the extended C-terminus was constructed and overexpressed in Escherichia coli. The conformational characteristics of M-CaLP were studied by CD and fluorescence spectroscopy and compared with those of the oyster CaM and CaLP. The far-UV CD results reveal that the extra tail has a strong effect on the Ca(2+)-induced, but a relatively weak effect on the Mg(2+)-induced conformational changes in CaLP. However, upon Ca2+ or Mg2+ binding, only slight changes for intrinsic phenylalanine and tyrosine fluorescence spectra between M-CaLP and CaLP are observed. Our results also indicate that the extra tail can significantly decrease the exposure of the hydrophobic patches in CaLP. Additionally, affinity chromatography demonstrates that the target binding of CaLP is greatly influenced by its additional tail. All our results implicate that the extra tail may play some important roles in the interactions between CaLP and its targets in vivo.
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Affiliation(s)
- Shuo Li
- Institute of Marine Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, China
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Kanski J, Schöneich C. Protein nitration in biological aging: proteomic and tandem mass spectrometric characterization of nitrated sites. Methods Enzymol 2005; 396:160-71. [PMID: 16291231 DOI: 10.1016/s0076-6879(05)96016-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Proteomic techniques for the identification of 3-nitrotyrosine-containing proteins in various biological systems are described with emphasis on the direct mass spectrometric detection and sequencing of 3-nitrotyrosine-containing peptides. Strengths and weaknesses of various separation and mass spectrometric techniques are discussed. Some examples for the MS/MS analysis of nitrated peptides obtained from aging rat heart and skeletal muscle are provided, such as nitration of Tyr105 of the mitochondrial electron-transfer flavoprotein and Tyr14 of creatine kinase.
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Affiliation(s)
- Jaroslaw Kanski
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, USA
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Abstract
Modern mass spectrometry (MS) is well known for its exquisite sensitivity in probing the covalent structure of macromolecules, and for that reason, it has become the major tool used to identify individual proteins in proteomics studies. This use of MS is now widespread and routine. In addition to this application of MS, a handful of laboratories are developing and using a methodology by which MS can be used to probe protein conformation and dynamics. This application involves using MS to analyze amide hydrogen/deuterium (H/D) content from exchange experiments. Introduced by Linderstøm-Lang in the 1950s, H/D exchange involves using (2)H labeling to probe the rate at which protein backbone amide protons undergo chemical exchange with the protons of water. With the advent of highly sensitive electrospray ionization (ESI)-MS, a powerful new technique for measuring H/D exchange in proteins at unprecedented sensitivity levels also became available. Although it is still not routine, over the past decade the methodology has been developed and successfully applied to study various proteins and it has contributed to an understanding of the functional dynamics of those proteins.
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Affiliation(s)
- Claudia S Maier
- Department of Chemistry, Oregon State University, Corvallis, Oregon, USA
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