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Kahraman K, Robson SA, Göcenler O, Yenici CM, Tozkoparan CD, Klein JM, Dötsch V, Elgin ES, Haas AL, Ziarek JJ, Dağ Ç. Characterizing the monomer-dimer equilibrium of UbcH8/Ube2L6: A combined SAXS and NMR study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.13.536743. [PMID: 37090523 PMCID: PMC10120734 DOI: 10.1101/2023.04.13.536743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Interferon-stimulated gene-15 (ISG15) is an interferon-induced protein with two ubiquitin-like (Ubl) domains linked by a short peptide chain, and the conjugated protein of the ISGylation system. Similar to ubiquitin and other Ubls, ISG15 is ligated to its target proteins through a series of E1, E2, and E3 enzymes known as Uba7, Ube2L6/UbcH8, and HERC5, respectively. Ube2L6/UbcH8 plays a literal central role in ISGylation, underscoring it as an important drug target for boosting innate antiviral immunity. Depending on the type of conjugated protein and the ultimate target protein, E2 enzymes have been shown to function as monomers, dimers, or both. UbcH8 has been crystalized in both monomeric and dimeric forms, but the functional state is unclear. Here, we used a combined approach of small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) spectroscopy to characterize UbcH8's oligomeric state in solution. SAXS revealed a dimeric UbcH8 structure that could be dissociated when fused N-terminally to glutathione S-transferase. NMR spectroscopy validated the presence of a concentration-dependent monomer-dimer equilibrium and suggested a backside dimerization interface. Chemical shift perturbation and peak intensity analysis further suggest dimer-induced conformational dynamics at E1 and E3 interfaces - providing hypotheses for the protein's functional mechanisms. Our study highlights the power of combining NMR and SAXS techniques in providing structural information about proteins in solution.
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Affiliation(s)
- Kerem Kahraman
- Nanofabrication and Nanocharacterization Center for Scientific and Technological Advanced Research (nSTAR), Koc University, İstanbul, Turkey
| | - Scott A. Robson
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 East Superior Avenue, Chicago, IL, 460611, USA
| | - Oktay Göcenler
- Nanofabrication and Nanocharacterization Center for Scientific and Technological Advanced Research (nSTAR), Koc University, İstanbul, Turkey
| | - Cansu M. Yenici
- Nanofabrication and Nanocharacterization Center for Scientific and Technological Advanced Research (nSTAR), Koc University, İstanbul, Turkey
| | - Cansu D. Tozkoparan
- Nanofabrication and Nanocharacterization Center for Scientific and Technological Advanced Research (nSTAR), Koc University, İstanbul, Turkey
| | - Jennifer M. Klein
- Department of Biochemistry and Molecular Biology, LSUHSC-School of Medicine, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Volker Dötsch
- Centre for Biomolecular Magnetic Resonance, Institute for Biophysical Chemistry, Goethe-University of Frankfurt/Main, Germany
| | - Emine Sonay Elgin
- Muğla Sıtkı Koçman University, College of Sciences, Department of Chemistry, Mugla, 48000, Turkey
| | - Arthur L. Haas
- Department of Biochemistry and Molecular Biology, LSUHSC-School of Medicine, 1901 Perdido Street, New Orleans, LA, 70112, USA
| | - Joshua J. Ziarek
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, 320 East Superior Avenue, Chicago, IL, 460611, USA
| | - Çağdaş Dağ
- Nanofabrication and Nanocharacterization Center for Scientific and Technological Advanced Research (nSTAR), Koc University, İstanbul, Turkey
- Koc University Isbank Center for Infectious Diseases (KUISCID), Koc University, Istanbul, Turkey
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2
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Novak D, Mojovic M, Pavicevic A, Zatloukalova M, Hernychova L, Bartosik M, Vacek J. Electrochemistry and electron paramagnetic resonance spectroscopy of cytochrome c and its heme-disrupted analogs. Bioelectrochemistry 2018; 119:136-141. [DOI: 10.1016/j.bioelechem.2017.09.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/19/2017] [Accepted: 09/19/2017] [Indexed: 11/30/2022]
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3
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Gupta S, Feng J, Chan LJG, Petzold CJ, Ralston CY. Synchrotron X-ray footprinting as a method to visualize water in proteins. JOURNAL OF SYNCHROTRON RADIATION 2016; 23:1056-69. [PMID: 27577756 PMCID: PMC5006651 DOI: 10.1107/s1600577516009024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 06/03/2016] [Indexed: 05/23/2023]
Abstract
The vast majority of biomolecular processes are controlled or facilitated by water interactions. In enzymes, regulatory proteins, membrane-bound receptors and ion-channels, water bound to functionally important residues creates hydrogen-bonding networks that underlie the mechanism of action of the macromolecule. High-resolution X-ray structures are often difficult to obtain with many of these classes of proteins because sample conditions, such as the necessity of detergents, often impede crystallization. Other biophysical techniques such as neutron scattering, nuclear magnetic resonance and Fourier transform infrared spectroscopy are useful for studying internal water, though each has its own advantages and drawbacks, and often a hybrid approach is required to address important biological problems associated with protein-water interactions. One major area requiring more investigation is the study of bound water molecules which reside in cavities and channels and which are often involved in both the structural and functional aspects of receptor, transporter and ion channel proteins. In recent years, significant progress has been made in synchrotron-based radiolytic labeling and mass spectroscopy techniques for both the identification of bound waters and for characterizing the role of water in protein conformational changes at a high degree of spatial and temporal resolution. Here the latest developments and future capabilities of this method for investigating water-protein interactions and its synergy with other synchrotron-based methods are discussed.
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Affiliation(s)
- Sayan Gupta
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jun Feng
- Experimental Systems, Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Leanne Jade G. Chan
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Christopher J. Petzold
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Corie Y. Ralston
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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4
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Oxidative footprinting in the study of structure and function of membrane proteins: current state and perspectives. Biochem Soc Trans 2016; 43:983-94. [PMID: 26517913 DOI: 10.1042/bst20150130] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Membrane proteins, such as receptors, transporters and ion channels, control the vast majority of cellular signalling and metabolite exchange processes and thus are becoming key pharmacological targets. Obtaining structural information by usage of traditional structural biology techniques is limited by the requirements for the protein samples to be highly pure and stable when handled in high concentrations and in non-native buffer systems, which is often difficult to achieve for membrane targets. Hence, there is a growing requirement for the use of hybrid, integrative approaches to study the dynamic and functional aspects of membrane proteins in physiologically relevant conditions. In recent years, significant progress has been made in the field of oxidative labelling techniques and in particular the X-ray radiolytic footprinting in combination with mass spectrometry (MS) (XF-MS), which provide residue-specific information on the solvent accessibility of proteins. In combination with both low- and high-resolution data from other structural biology approaches, it is capable of providing valuable insights into dynamics of membrane proteins, which have been difficult to obtain by other structural techniques, proving a highly complementary technique to address structure and function of membrane targets. XF-MS has demonstrated a unique capability for identification of structural waters and conformational changes in proteins at both a high degree of spatial and a high degree of temporal resolution. Here, we provide a perspective on the place of XF-MS among other structural biology methods and showcase some of the latest developments in its usage for studying water-mediated transmembrane (TM) signalling, ion transport and ligand-induced allosteric conformational changes in membrane proteins.
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5
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O'Dell WB, Bodenheimer AM, Meilleur F. Neutron protein crystallography: A complementary tool for locating hydrogens in proteins. Arch Biochem Biophys 2016; 602:48-60. [DOI: 10.1016/j.abb.2015.11.033] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/12/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022]
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6
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Structure and dynamics of protein waters revealed by radiolysis and mass spectrometry. Proc Natl Acad Sci U S A 2012; 109:14882-7. [PMID: 22927377 DOI: 10.1073/pnas.1209060109] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Water is critical for the structure, stability, and functions of macromolecules. Diffraction and NMR studies have revealed structure and dynamics of bound waters at atomic resolution. However, localizing the sites and measuring the dynamics of bound waters, particularly on timescales relevant to catalysis and macromolecular assembly, is quite challenging. Here we demonstrate two techniques: first, temperature-dependent radiolytic hydroxyl radical labeling with a mass spectrometry (MS)-based readout to identify sites of bulk and bound water interactions with surface and internal residue side chains, and second, H(2)(18)O radiolytic exchange coupled MS to measure the millisecond dynamics of bound water interactions with various internal residue side chains. Through an application of the methods to cytochrome c and ubiquitin, we identify sites of water binding and measure the millisecond dynamics of bound waters in protein crevices. As these MS-based techniques are very sensitive and not protein size limited, they promise to provide unique insights into protein-water interactions and water dynamics for both small and large proteins and their complexes.
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7
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Krishtalik LI. The medium reorganization energy for the charge transfer reactions in proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1444-56. [DOI: 10.1016/j.bbabio.2011.07.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 06/30/2011] [Accepted: 07/04/2011] [Indexed: 10/18/2022]
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8
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Waldeck DH, Khoshtariya DE. Fundamental Studies of Long- and Short-Range Electron Exchange Mechanisms between Electrodes and Proteins. MODERN ASPECTS OF ELECTROCHEMISTRY 2011. [DOI: 10.1007/978-1-4614-0347-0_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Ye S, Markelz A. Hydration Effects on Energy Relaxation of Ferric Cytochrome C Films after Soret-Band Photoexcitation. J Phys Chem B 2010; 114:15151-7. [DOI: 10.1021/jp104217j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Shuji Ye
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China 230026, and Department of Physics, University at Buffalo, SUNY, 239 Fronczak Hall, Buffalo, New York 14260-1500, United States
| | - Andrea Markelz
- Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China 230026, and Department of Physics, University at Buffalo, SUNY, 239 Fronczak Hall, Buffalo, New York 14260-1500, United States
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10
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Davis KL, Waldeck DH. Effect of Deuterium Substitution on Electron Transfer at Cytochrome c/SAM Interfaces. J Phys Chem B 2008; 112:12498-507. [DOI: 10.1021/jp803006b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kathryn L. Davis
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - David H. Waldeck
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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11
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Bánó M, Marek J. How thick is the layer of thermal volume surrounding the protein? Biophys Chem 2005; 120:44-54. [PMID: 16242836 DOI: 10.1016/j.bpc.2005.09.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Revised: 09/23/2005] [Accepted: 09/25/2005] [Indexed: 10/25/2022]
Abstract
Investigation on the volume properties of protein hydration layers is reported. Presented results are based on combination of Monte Carlo modeling and available experimental data. Six globular proteins with known data are chosen for analysis. Analyzing the model and the experimental results we found that water molecules bound to proteins by hydrogen bond are preferentially located at the places with local depressions on the protein surface. Consequently, the hydration level is not strictly proportional to the area of charged and polar surfaces, but also depends on the shape of the molecular surface. The thickness of the thermal volume layer as calculated in the framework of the scaled particle theory is 0.6-0.65 A for chosen proteins. The obtained value is significantly lower than that presented for proteins in earlier papers (where proportionality between the hydration level and the area of charged and polar surfaces was assumed), but is close to the value published for small solute molecules. Discussion including the influence of protein size and the thermal motion of the surface is presented.
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Affiliation(s)
- Mikulás Bánó
- Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04353 Kosice, Slovak Republic.
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12
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Mobility Studies in Proteins by 15N Nuclear Magnetic Resonance: Rusticyanin as an Example. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/978-3-662-08722-0_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
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13
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Bánó M, Marek J, Stupák M. Hydrodynamic parameters of hydrated macromolecules: Monte Carlo calculation. Phys Chem Chem Phys 2004. [DOI: 10.1039/b315620f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Jiménez B, Piccioli M, Moratal JM, Donaire A. Backbone dynamics of rusticyanin: the high hydrophobicity and rigidity of this blue copper protein is responsible for its thermodynamic properties. Biochemistry 2003; 42:10396-405. [PMID: 12950166 DOI: 10.1021/bi034692q] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Local dynamics and solute-solvent exchange properties of rusticyanin (Rc) from Thiobacillus ferrooxidans have been studied by applying heteronuclear ((1)H, (15)N) NMR spectroscopy. (15)N relaxation parameters have been determined for the reduced protein, and a model-free analysis has been applied. The high average value of the generalized order parameter, S(2) (0.93), indicates that Rc is very rigid. The analysis of cross correlation rates recorded in both the reduced and the oxidized forms conclusively proves that Rc possesses the same dynamic features in both oxidation states. The accessibility of backbone amide protons to the solvent at different time scales has also been studied by applying specific heteronuclear pulse sequences and by H(2)O/D(2)O exchange experiments. These experiments reveal that rusticyanin is extremely hydrophobic. The first N-35 amino acids, not present in the other BCPs, protect the beta-barrel core from its interaction with the solvent, and thus, this is one of the main factors contributing to the hydrophobicity. Both characteristics (high rigidity and hydrophobicity) are maintained in the metal ion surroundings.
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Affiliation(s)
- Beatriz Jiménez
- Departamento de Química Inorgánica, Universitat de València, Burjassot, Spain
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15
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Khoshtariya DE, Wei J, Liu H, Yue H, Waldeck DH. Charge-transfer mechanism for cytochrome c adsorbed on nanometer thick films. Distinguishing frictional control from conformational gating. J Am Chem Soc 2003; 125:7704-14. [PMID: 12812512 DOI: 10.1021/ja034719t] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using nanometer thick tunneling barriers with specifically attached cytochrome c, the electron-transfer rate constant was studied as a function of the SAM composition (alkane versus terthiophene), the omega-terminating group type (pyridine, imidazole, nitrile), and the solution viscosity. At large electrode-reactant separations, the pyridine terminated alkanethiols exhibit an exponential decline of the rate constant with increasing electron-transfer distance. At short separations, a plateau behavior, analogous to systems involving -COOH terminal groups to which cytochrome c can be attached electrostatically, is observed. The dependence of the rate constant in the plateau region on system properties is investigated. The rate constant is insensitive to the mode of attachment to the surface but displays a significant viscosity dependence, change with spacer composition (alkane versus terthiophene), and nature of the solvent (H(2)O versus D(2)O). Based on these findings and others, the conclusion is drawn that the charge-transfer rate constant at short distance is determined by polarization relaxation processes in the structure, rather than the electron tunneling probability or large-amplitude conformational rearrangement (gating). The transition in reaction mechanism with distance reflects a gradual transition between the tunneling and frictional mechanisms. This conclusion is consistent with data from a number of other sources as well.
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16
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Bertini I, Ghosh K, Rosato A, Vasos PR. A high-resolution NMR study of long-lived water molecules in both oxidation states of a minimal cytochrome c. Biochemistry 2003; 42:3457-63. [PMID: 12653549 DOI: 10.1021/bi0272961] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interaction of water with oxidized and reduced cytochrome c from the Gram-positive bacterium Bacillus pasteurii (a 71-amino acid long monoheme cytochrome) is investigated through CLEANEX experiments and (15)N-edited ePHOGSY and Tr-ROESY experiments. It appears that a water molecule gives rise to dipolar cross-relaxation with the amide protons of Gly74 and Ile75, with a residence time longer than 0.4 ns, to account for a negative NOE. Such water molecule is present in both the oxidized and reduced species and in the X-ray structure. It appears to have a structural role. Other possible roles are discussed by comparison with the water molecules present in other c-type cytochromes. The amide proton of Cys35 is found to exchange rapidly with the solvent in the oxidized but not in the reduced protein, at variance with H/D exchange experiments, which probe a different time scale. The present data confirm that electron-transfer proteins evolved to minimize reorganization energy upon change of the oxidation state, even though the consequent variation of charge of the metal ion may induce some changes in the structure and/or dynamics of the protein.
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Affiliation(s)
- Ivano Bertini
- Magnetic Resonance Center (CERM), University of Florence, Via L. Sacconi 6, 50019 Sesto Fiorentino, Italy.
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17
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Bertini I, Luchinat C, Nerinovski K, Parigi G, Cross M, Xiao Z, Wedd AG. Application of NMRD to hydration of rubredoxin and a variant containing a (Cys-S)3FeIII(OH) site. Biophys J 2003; 84:545-51. [PMID: 12524306 PMCID: PMC1302634 DOI: 10.1016/s0006-3495(03)74873-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hydration of oxidized rubredoxin (Fe(III)(S-Cys)(4) center) was investigated by (1)H and (17)O relaxation measurements of bulk water as a function of the applied magnetic field (nuclear magnetic relaxation dispersion). Oxidized rubredoxin showed an increased water (1)H relaxation profile with respect to the diamagnetic gallium derivative or reduced species. Analysis of the data shows evidence of exchangeable proton(s) approximately 4.0-4.5 A from the metal ion, the exchange time being longer than 10(-10) s and shorter than 10(-5) s. The correlation time for the proton-electrons interaction is 7 x 10(-11) s and is attributed to the effective electron relaxation time. Its magnitude is consistent with the large signal linewidths of the protein donor nuclei, observed in high resolution NMR spectra. For reduced rubredoxin, such correlation time is proposed to be smaller than 10(-11) s. (17)O relaxation measurements suggest the presence of at least one long-lived protein-bound water molecule. Analogous relaxation measurements were performed on the C6S rubredoxin variant, whose iron(III) center has been previously shown to be coordinated to three cysteine residues and a hydroxide ion above pH 6. (1)H nuclear magnetic relaxation dispersion profiles indicate increased hydration with respect to the wild-type.
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Affiliation(s)
- Ivano Bertini
- CERM and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy.
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Abstract
Protein-water interactions are key to biological function. They have an underlying dynamic component that pervades the functional roles associated both with particular systems and with the properties of proteins in general. This article focuses on the specific ways in which the dynamics of water are important to protein structure, motion and adaptability to changes in the protein environment.
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Affiliation(s)
- Carla Mattos
- Dept Molecular and Structural Biochemistry, North Carolina State University, 128 Polk Hall, Raleigh, NC 27695-7622, USA.
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Bertini I, Hajieva P, Luchinat C, Nerinovski K. Redox-dependent hydration of cytochrome c and cytochrome b(5) studied through (17)O NMRD. J Am Chem Soc 2001; 123:12925-6. [PMID: 11749561 DOI: 10.1021/ja0163624] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- I Bertini
- CERM, Magnetic Resonance Center, University of Florence, Via Luigi Sacconi 6, 50019 Sesto Fiorentino, Italy
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20
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Bertini I, Bryant DA, Ciurli S, Dikiy A, Fernández CO, Luchinat C, Safarov N, Vila AJ, Zhao J. Backbone dynamics of plastocyanin in both oxidation states. Solution structure of the reduced form and comparison with the oxidized state. J Biol Chem 2001; 276:47217-26. [PMID: 11509552 DOI: 10.1074/jbc.m100304200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A model-free analysis based on (15)N R(1), (15)N R(2), and (15)N-(1)H nuclear Overhauser effects was performed on reduced (diamagnetic) and oxidized (paramagnetic) forms of plastocyanin from Synechocystis sp. PCC6803. The protein backbone is rigid, displaying a small degree of mobility in the sub-nanosecond time scale. The loops surrounding the copper ion, involved in physiological electron transfer, feature a higher extent of flexibility in the longer time scale in both redox states, as measured from D(2)O exchange of amide protons and from NH-H(2)O saturation transfer experiments. In contrast to the situation for other electron transfer proteins, no significant difference in the dynamic properties is found between the two redox forms. A solution structure was also determined for the reduced plastocyanin and compared with the solution structure of the oxidized form in order to assess possible structural changes related to the copper ion redox state. Within the attained resolution, the structure of the reduced plastocyanin is indistinguishable from that of the oxidized form, even though small chemical shift differences are observed. The present characterization provides information on both the structural and dynamic behavior of blue copper proteins in solution that is useful to understand further the role(s) of protein dynamics in electron transfer processes.
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Affiliation(s)
- I Bertini
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi, 6-50019 Sesto Fiorentino, Italy
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21
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Affiliation(s)
- I Bertini
- Magnetic Resonance Center (CERM), University of Florence, Florence 50019, Italy
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