1
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Jenney FE, Wang H, George SJ, Xiong J, Guo Y, Gee LB, Marizcurrena JJ, Castro-Sowinski S, Staskiewicz A, Yoda Y, Hu MY, Tamasaku K, Nagasawa N, Li L, Matsuura H, Doukov T, Cramer SP. Temperature-dependent iron motion in extremophile rubredoxins - no need for 'corresponding states'. Sci Rep 2024; 14:12197. [PMID: 38806591 PMCID: PMC11133467 DOI: 10.1038/s41598-024-62261-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 05/15/2024] [Indexed: 05/30/2024] Open
Abstract
Extremophile organisms are known that can metabolize at temperatures down to - 25 °C (psychrophiles) and up to 122 °C (hyperthermophiles). Understanding viability under extreme conditions is relevant for human health, biotechnological applications, and our search for life elsewhere in the universe. Information about the stability and dynamics of proteins under environmental extremes is an important factor in this regard. Here we compare the dynamics of small Fe-S proteins - rubredoxins - from psychrophilic and hyperthermophilic microorganisms, using three different nuclear techniques as well as molecular dynamics calculations to quantify motion at the Fe site. The theory of 'corresponding states' posits that homologous proteins from different extremophiles have comparable flexibilities at the optimum growth temperatures of their respective organisms. Although 'corresponding states' would predict greater flexibility for rubredoxins that operate at low temperatures, we find that from 4 to 300 K, the dynamics of the Fe sites in these homologous proteins are essentially equivalent.
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Affiliation(s)
- Francis E Jenney
- Georgia Campus, Philadelphia College of Osteopathic Medicine, Suwanee, GA, 30024, USA
| | | | | | - Jin Xiong
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Leland B Gee
- LCLS, SLAC National Laboratory, Stanford, CA, 94025, USA
| | | | | | - Anna Staskiewicz
- Georgia Campus, Philadelphia College of Osteopathic Medicine, Suwanee, GA, 30024, USA
| | - Yoshitaka Yoda
- Precision Spectroscopy Division, SPring-8/JASRI, Sayo, Hyogo, 679-5198, Japan
| | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL, 60439, USA
| | | | - Nobumoto Nagasawa
- Precision Spectroscopy Division, SPring-8/JASRI, Sayo, Hyogo, 679-5198, Japan
| | - Lei Li
- Synchrotron Radiation Research Center, Hyogo, 679-5165, Japan
| | | | - Tzanko Doukov
- SSRL, SLAC National Laboratory, Stanford, CA, 94025, USA
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2
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Di Rocco G, Battistuzzi G, Borsari M, Bortolotti CA, Ranieri A, Sola M. The enthalpic and entropic terms of the reduction potential of metalloproteins: Determinants and interplay. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214071] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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3
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 549] [Impact Index Per Article: 54.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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4
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Niu S, Ichiye T. Density functional theory calculations of redox properties of iron–sulphur protein analogues. MOLECULAR SIMULATION 2011. [DOI: 10.1080/08927022.2011.582111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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5
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Borreguero JM, He J, Meilleur F, Weiss KL, Brown CM, Myles DA, Herwig KW, Agarwal PK. Redox-promoting protein motions in rubredoxin. J Phys Chem B 2011; 115:8925-36. [PMID: 21608980 DOI: 10.1021/jp201346x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Proteins are dynamic objects, constantly undergoing conformational fluctuations, yet the linkage between internal protein motion and function is widely debated. This study reports on the characterization of temperature-activated collective and individual atomic motions of oxidized rubredoxin, a small 53 residue protein from thermophilic Pyrococcus furiosus (RdPf). Computational modeling allows detailed investigations of protein motions as a function of temperature, and neutron scattering experiments are used to compare to computational results. Just above the dynamical transition temperature which marks the onset of significant anharmonic motions of the protein, the computational simulations show both a significant reorientation of the average electrostatic force experienced by the coordinated Fe(3+) ion and a dramatic rise in its strength. At higher temperatures, additional anharmonic modes become activated and dominate the electrostatic fluctuations experienced by the ion. At 360 K, close to the optimal growth temperature of P. furiosus, simulations show that three anharmonic modes including motions of two conserved residues located at the protein active site (Ile7 and Ile40) give rise to the majority of the electrostatic fluctuations experienced by the Fe(3+) ion. The motions of these residues undergo displacements which may facilitate solvent access to the ion.
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Affiliation(s)
- Jose M Borreguero
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
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6
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Perrin BS, Ichiye T. Fold versus sequence effects on the driving force for protein-mediated electron transfer. Proteins 2011; 78:2798-808. [PMID: 20635418 DOI: 10.1002/prot.22794] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Electron transport chains composed of electron transfer reactions mainly between proteins provide fast efficient flow of energy in a variety of metabolic pathways. Reduction potentials are essential characteristics of the proteins because they determine the driving forces for the electron transfers. As both polar and charged groups from the backbone and side chains define the electrostatic environment, both the fold and the sequence will contribute. However, although the role of a specific sequence may be determined by experimental mutagenesis studies of reduction potentials, understanding the role of the fold by experiment is much more difficult. Here, continuum electrostatics and density functional theory calculations are used to analyze reduction potentials in [4Fe-4S] proteins. A key feature is that multiple homologous proteins in three different folds are compared: six high potential iron-sulfur proteins, four bacterial ferredoxins, and four nitrogenase iron proteins. Calculated absolute reduction potentials are shown to be in quantitative agreement with electrochemical reduction potentials. Calculations further demonstrate that the contribution of the backbone is larger than that of the side chains and is consistent for homologous proteins but differs for nonhomologous proteins, indicating that the fold is the major protein factor determining the reduction potential, whereas the specific amino acid sequence tunes the reduction potential for a given fold. Moreover, the fold contribution is determined mainly by the proximity of the redox site to the protein surface and the orientation of the dipoles of backbone near the redox site.
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Affiliation(s)
- Bradley Scott Perrin
- Department of Chemistry, Georgetown University, Box 571227, Washington, District of Columbia 20057-1227, USA
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7
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Gamiz-Hernandez AP, Kieseritzky G, Ishikita H, Knapp EW. Rubredoxin Function: Redox Behavior from Electrostatics. J Chem Theory Comput 2011; 7:742-52. [DOI: 10.1021/ct100476h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ana Patricia Gamiz-Hernandez
- Institute of Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Fabeckstrasse 36a, D-14195, Berlin, Germany
| | - Gernot Kieseritzky
- Institute of Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Fabeckstrasse 36a, D-14195, Berlin, Germany
| | - Hiroshi Ishikita
- Career-Path Promotion Unit for Young Life Scientists, Kyoto University, 202 Building E, Graduate School of Medicine, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - E. W. Knapp
- Institute of Chemistry and Biochemistry, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Fabeckstrasse 36a, D-14195, Berlin, Germany
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8
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Luo Y, Ergenekan CE, Fischer JT, Tan ML, Ichiye T. The molecular determinants of the increased reduction potential of the rubredoxin domain of rubrerythrin relative to rubredoxin. Biophys J 2010; 98:560-8. [PMID: 20159152 DOI: 10.1016/j.bpj.2009.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 11/28/2022] Open
Abstract
Based on the crystal structures, three possible sequence determinants have been suggested as the cause of a 285 mV increase in reduction potential of the rubredoxin domain of rubrerythrin over rubredoxin by modulating the polar environment around the redox site. Here, electrostatic calculations of crystal structures of rubredoxin and rubrerythrin and molecular dynamics simulations of rubredoxin wild-type and mutants are used to elucidate the contributions to the increased reduction potential. Asn(160) and His(179) in rubrerythrin versus valines in rubredoxins are predicted to be the major contributors, as the polar side chains contribute significantly to the electrostatic potential in the redox site region. The mutant simulations show both side chains rotating on a nanosecond timescale between two conformations with different electrostatic contributions. Reduction also causes a change in the reduction energy that is consistent with a linear response due to the interesting mechanism of shifting the relative populations of the two conformations. In addition to this, a simulation of a triple mutant indicates the side-chain rotations are approximately anticorrelated so whereas one is in the high potential conformation, the other is in the low potential conformation. However, Ala(176) in rubrerythrin versus a leucine in rubredoxin is not predicted to be a large contributor, because the solvent accessibility increases only slightly in mutant simulations and because it is buried in the interface of the rubrerythrin homodimer.
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Affiliation(s)
- Yan Luo
- Department of Chemistry, Georgetown University, Washington, District of Columbia, USA
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9
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Tatur J, Hagen WR, Heering HA. Voltammetry of Pyrococcus furiosus ferritin: dependence of iron release rate on mediator potential. Dalton Trans 2009:2837-42. [PMID: 19333508 DOI: 10.1039/b819775j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electrocatalytic iron release from P. furiosus ferritin upon reduction with a series of electron mediators was studied. The observed iron release rate as a function of mediator midpoint potentials is described by a two-step model, in which electron transfer from the mediator to ferritin is rate limiting at low driving force, and the protein's overall catalytic rate of k(cat)= 701 electrons per s is limiting at high driving force (low mediator potentials). The upper limit of the mediator potential at which the reductive iron release activity of P. furiosus ferritin has been observed in the electrochemical cell is -47 mV vs. SHE.
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Affiliation(s)
- Jana Tatur
- Division of Molecular Biosciences, Imperial College, London, UK SW7 2AZ
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10
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LeBard DN, Matyushov DV. Redox entropy of plastocyanin: Developing a microscopic view of mesoscopic polar solvation. J Chem Phys 2008; 128:155106. [DOI: 10.1063/1.2904879] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Niu S, Wang XB, Nichols JA, Wang LS, Ichiye T. Combined Quantum Chemistry and Photoelectron Spectroscopy Study of the Electronic Structure and Reduction Potentials of Rubredoxin Redox Site Analogues. J Phys Chem A 2003. [DOI: 10.1021/jp034316f] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shuqiang Niu
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Xue-Bin Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Jeffrey A. Nichols
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Lai-Sheng Wang
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
| | - Toshiko Ichiye
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, Department of Physics, Washington State University, 2710 University Drive, Richland, Washington 99352, and W. R. Wiley Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352
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12
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Grottesi A, Ceruso MA, Colosimo A, Di Nola A. Molecular dynamics study of a hyperthermophilic and a mesophilic rubredoxin. Proteins 2002; 46:287-94. [PMID: 11835504 DOI: 10.1002/prot.10045] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In recent years, increased interest in the origin of protein thermal stability has gained attention both for its possible role in understanding the forces governing the folding of a protein and for the design of new highly stable engineered biocatalysts. To study the origin of thermostability, we have performed molecular dynamics simulations of two rubredoxins, from the mesophile Clostridium pasteurianum and from the hyperthermophile Pyrococcus furiosus. The simulations were carried out at two temperatures, 300 and 373 K, for each molecule. The length of the simulations was within the range of 6-7.2 ns. The rubredoxin from the hyperthermophilic organism was more flexible than its mesophilic counterpart at both temperatures; however, the overall flexibility of both molecules at their optimal growth temperature was the same, despite 59% sequence homology. The conformational space sampled by both molecules was larger at 300 K than at 373 K. The essential dynamics analysis showed that the principal overall motions of the two molecules are significantly different. On the contrary, each molecule showed similar directions of motion at both temperatures.
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Affiliation(s)
- Alessandro Grottesi
- Department of Biochemical Sciences, University of Rome, La Sapienza, Rome, Italy.
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13
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Affiliation(s)
- F E Jenney
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
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14
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Min T, Ergenekan CE, Eidsness MK, Ichiye T, Kang C. Leucine 41 is a gate for water entry in the reduction of Clostridium pasteurianum rubredoxin. Protein Sci 2001; 10:613-21. [PMID: 11344329 PMCID: PMC2374124 DOI: 10.1110/gad.34501] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Biological electron transfer is an efficient process even though the distances between the redox moieties are often quite large. It is therefore of great interest to gain an understanding of the physical basis of the rates and driving forces of these reactions. The structural relaxation of the protein that occurs upon change in redox state gives rise to the reorganizational energy, which is important in the rates and the driving forces of the proteins involved. To determine the structural relaxation in a redox protein, we have developed methods to hold a redox protein in its final oxidation state during crystallization while maintaining the same pH and salt conditions of the crystallization of the protein in its initial oxidation state. Based on 1.5 A resolution crystal structures and molecular dynamics simulations of oxidized and reduced rubredoxins (Rd) from Clostridium pasteurianum (Cp), the structural rearrangements upon reduction suggest specific mechanisms by which electron transfer reactions of rubredoxin should be facilitated. First, expansion of the [Fe-S] cluster and concomitant contraction of the NH...S hydrogen bonds lead to greater electrostatic stabilization of the extra negative charge. Second, a gating mechanism caused by the conformational change of Leucine 41, a nonpolar side chain, allows transient penetration of water molecules, which greatly increases the polarity of the redox site environment and also provides a source of protons. Our method of producing crystals of Cp Rd from a reducing solution leads to a distribution of water molecules not observed in the crystal structure of the reduced Rd from Pyrococcus furiosus. How general this correlation is among redox proteins must be determined in future work. The combination of our high-resolution crystal structures and molecular dynamics simulations provides a molecular picture of the structural rearrangement that occurs upon reduction in Cp rubredoxin.
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Affiliation(s)
- T Min
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4660, USA
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15
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Dvorsky R, Sevcik J, Caves LSD, Hubbard RE, Verma CS. Temperature Effects on Protein Motions: A Molecular Dynamics Study of RNase-Sa. J Phys Chem B 2000. [DOI: 10.1021/jp001933k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Reipa V, Holden MJ, Mayhew MP, Vilker VL. Temperature dependence of the formal reduction potential of putidaredoxin. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1459:1-9. [PMID: 10924895 DOI: 10.1016/s0005-2728(00)00108-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Putidaredoxin (Pdx), a [2Fe-2S] redox protein of size M(r) 11,600, transfers two electrons in two separate steps from the flavin containing putidaredoxin reductase to the heme protein, cytochrome CYP101 in the P450cam catalytic cycle. It has recently come to light, through NMR measurements, that there can be appreciable differences in the Pdx conformational dynamics between its reduced and oxidized states. The redox reaction entropy, deltaS(0')rc = (S(0')Pdx(r)-S(0')Pdx(0)), as determined from measurements of the variation in formal potential with temperature, E0'(T), provides a measure of the strength of this influence on Pdx function. We designed a spectroelectrochemical cell using optically transparent tin oxide electrodes, without fixed or diffusible mediators, to measure E0'(T) over the temperature range 0-40 degrees C. The results indicate that the redox reaction entropy for Pdx is biphasic, decreasing from -213 +/- 27 J mol(-1) K(-1) over 0-27 degrees C, to -582 +/- 150 J mol(-1) K (-1) over 27-40 degrees C. These redox reaction entropy changes are significantly more negative than the changes reported for most cytochromes, although our measurement over the temperature interval 0-27 degrees C is in the range reported for other iron-sulfur proteins. This suggests that Pdx (and other ferredoxins) is a less rigid system than monohemes, and that redox-linked changes in conformation, and/or conformational dynamics, impart to these proteins the ability to interact with a number of redox partners.
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Affiliation(s)
- V Reipa
- Biotechnology Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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17
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Yoon KS, Hille R, Hemann C, Tabita FR. Rubredoxin from the green sulfur bacterium Chlorobium tepidum functions as an electron acceptor for pyruvate ferredoxin oxidoreductase. J Biol Chem 1999; 274:29772-8. [PMID: 10514453 DOI: 10.1074/jbc.274.42.29772] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rubredoxin (Rd) from the moderately thermophilic green sulfur bacterium Chlorobium tepidum was found to function as an electron acceptor for pyruvate ferredoxin oxidoreductase (PFOR). This enzyme, which catalyzes the conversion of pyruvate to acetyl-CoA and CO(2), exhibited an absolute dependence upon the presence of Rd. However, Rd was incapable of participating in the pyruvate synthase or CO(2) fixation reaction of C. tepidum PFOR, for which two different reduced ferredoxins are employed as electron donors. These results suggest a specific functional role for Rd in pyruvate oxidation and provide the initial indication that the two important physiological reactions catalyzed by PFOR/pyruvate synthase are dependent on different electron carriers in the cell. The UV-visible spectrum of oxidized Rd, with a monomer molecular weight of 6500, gave a molar absorption coefficient at 492 nm of 6.89 mM(-1) cm(-1) with an A(492)/A(280) ratio of 0.343 and contained one iron atom/molecule. Further spectroscopic studies indicated that the CD spectrum of oxidized C. tepidum Rd exhibited a unique absorption maximum at 385 nm and a shoulder at 420 nm. The EPR spectrum of oxidized Rd also exhibited unusual anisotropic resonances at g = 9.675 and g = 4.322, which is composed of a narrow central feature with broader shoulders to high and low field. The midpoint reduction potential of C. tepidum Rd was determined to be -87 mV, which is the most electronegative value reported for Rd from any source.
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Affiliation(s)
- K S Yoon
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210-1292, USA
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18
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Hagedoorn PL, Driessen MC, van den Bosch M, Landa I, Hagen WR. Hyperthermophilic redox chemistry: a re-evaluation. FEBS Lett 1998; 440:311-4. [PMID: 9872393 DOI: 10.1016/s0014-5793(98)01466-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The redox chemistry of Pyrococcus furiosus rubredoxin and ferredoxin has been studied as a function of temperature in direct voltammetry and in EPR monitored bulk titrations. The Ems of both proteins, measured with direct voltammetry, have a normal (linear) temperature dependence and show no pH dependence. EPR monitoring is not a reliable method to determine the temperature dependence of the Em: upon rapid freezing the proteins take their conformation corresponding to the freezing point of the solution.
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Affiliation(s)
- P L Hagedoorn
- Wageningen University and Research Centre, Department of Biomolecular Sciences, The Netherlands.
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19
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Lazaridis T, Lee I, Karplus M. Dynamics and unfolding pathways of a hyperthermophilic and a mesophilic rubredoxin. Protein Sci 1997; 6:2589-605. [PMID: 9416608 PMCID: PMC2143628 DOI: 10.1002/pro.5560061211] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Molecular dynamics simulations in solution are performed for a rubredoxin from the hyperthermophilic archaeon Pyrococcus furiosus (RdPf) and one from the mesophilic organism Desulfovibrio vulgaris (RdDv). The two proteins are simulated at four temperatures: 300 K, 373 K, 473 K (two sets), and 500 K; the various simulations extended from 200 ps to 1,020 ps. At room temperature, the two proteins are stable, remain close to the crystal structure, and exhibit similar dynamic behavior; the RMS residue fluctuations are slightly smaller in the hyperthermophilic protein. An analysis of the average energy contributions in the two proteins is made; the results suggest that the intraprotein energy stabilizes RdPf relative to RdDv. At 373 K, the mesophilic protein unfolds rapidly (it begins to unfold at 300 ps), whereas the hyperthermophilic does not unfold over the simulation of 600 ps. This is in accord with the expected stability of the two proteins. At 473 K, where both proteins are expected to be unstable, unfolding behavior is observed within 200 ps and the mesophilic protein unfolds faster than the hyperthermophilic one. At 500 K, both proteins unfold; the hyperthermophilic protein does so faster than the mesophilic protein. The unfolding behavior for the two proteins is found to be very similar. Although the exact order of events differs from one trajectory to another, both proteins unfold first by opening of the loop region to expose the hydrophobic core. This is followed by unzipping of the beta-sheet. The results obtained in the simulation are discussed in terms of the factors involved in flexibility and thermostability.
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Affiliation(s)
- T Lazaridis
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massacusetts 02138, USA
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20
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Deligiannakis Y, Boussac A, Bottin H, Perrier V, Bârzu O, Gilles AM. A new non-heme iron environment in Paracoccus denitrificans adenylate kinase studied by electron paramagnetic resonance and electron spin echo envelope modulation spectroscopy. Biochemistry 1997; 36:9446-52. [PMID: 9235989 DOI: 10.1021/bi970021e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Adenylate kinase from the Gram-negative bacterium Paracoccus denitrificans (AKden) has structural features highly similar to those of the enzyme from Gram-positive organisms. Atomic absorption spectroscopy of the recombinant protein, which is a dimer, revealed the presence of two metals, zinc and iron, each binding most probably to one monomer. Under oxidizing conditions, the electron paramagnetic resonance (EPR) spectrum of AKden at 4.2 K consists of features at g = 9.23, 4.34, 4.21, and 3.68. These features are absent in the ascorbate-reduced protein and are characteristic of a S = 5/2 spin system in a rhombic environment with E/D = 0.24 and are assigned to a non-heme Fe3+ (S = 5/2) center. The zero-field splitting parameter D (D = 1.4 +/- 0.2 cm-1) was estimated from the temperature dependence of the EPR spectra. These EPR characteristic as well as the difference absorption spectrum (oxidized minus reduced) of AKden are similar to those reported for the non-heme iron protein rubredoxin. Nevertheless, the redox potential of the Fe2+/Fe3+ couple in AKden was measured at +230 +/- 30 mV, which is more positive than the redox potential of the non-heme iron in rubredoxin. Binding of cyanide converts the iron from the high-spin (S = 5/2) to the low-spin (S = 1/2) spin state. The EPR spectrum of the non-heme Fe3+(S = 1/2) in the presence of cyanide has g values of 2.45, 2.18, and 1.92 and spin-Hamiltonian parameters R/lambda = 7. 4 and R/mu = 0.56. The conversion of the non-heme iron to the low-spin (S = 1/2) state allowed the study of its local environment by electron spin echo envelope modulation spectroscopy (ESEEM). The ESEEM data revealed the existence of 14N or 15N nuclei coupled to the low-spin iron after addition of KC14N or KC15N respectively. This demonstrated that iron in AKden has at least one labile coordination position that can be easily occupied by cyanide. Other possible magnetic interactions with nitrogen(s) from the protein are discussed.
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Affiliation(s)
- Y Deligiannakis
- Section de Bioénergétique, URA CNRS 2096, Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette, France
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