1
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Breglia R, Greco C, Fantucci P, De Gioia L, Bruschi M. Reactivation of the Ready and Unready Oxidized States of [NiFe]-Hydrogenases: Mechanistic Insights from DFT Calculations. Inorg Chem 2018; 58:279-293. [PMID: 30576127 DOI: 10.1021/acs.inorgchem.8b02348] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The apparently simple dihydrogen formation from protons and electrons (2H+ + 2e- ⇄ H2) is one of the most challenging reactions in nature. It is catalyzed by metalloenzymes of amazing complexity, called hydrogenases. A better understanding of the chemistry of these enzymes, especially that of the [NiFe]-hydrogenases subgroup, has important implications for production of H2 as alternative sustainable fuel. In this work, reactivation mechanism of the oxidized and inactive Ni-B and Ni-A states of the [NiFe]-hydrogenases active site has been investigated using density functional theory. Results obtained from this study show that one-electron reduction and protonation of the active site promote the removal of the bridging hydroxide ligand contained in Ni-B and Ni-A. However, this process is sufficient to activate only the Ni-B state. H2 binding to the active site is required to convert Ni-A to the active Ni-SIa state. Here, we also propose a reasonable structure for the spectroscopically well-characterized Ni-SIr and Ni-SU species, formed respectively from the one-electron reduction of Ni-B and Ni-A. Ni-SIr, depending on the pH at which the reaction occurs, features a bridging hydroxide ligand or a water molecule terminally coordinated to the Ni atom, whereas in Ni-SU a water molecule is terminally coordinated to the Fe atom, and the Cys64 residue is oxidized to sulfenate. The sulfenate oxygen atom in the Ni-A state affects the stereoelectronic properties of the binuclear cluster by modifying the coordination geometry of Ni, and consequently, by switching the regiochemistry of H2O and H2 binding from the Ni to the Fe atom. This effect is predicted to be at the origin of the different reactivation kinetics of the oxidized and inactive Ni-B and Ni-A states.
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2
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Zanello P. Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part II. [4Fe-4S] and [3Fe-4S] iron-sulfur proteins. J Struct Biol 2018; 202:250-263. [DOI: 10.1016/j.jsb.2018.01.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/11/2018] [Accepted: 01/29/2018] [Indexed: 01/27/2023]
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3
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Tai H, Xu L, Nishikawa K, Higuchi Y, Hirota S. Equilibrium between inactive ready Ni-SI r and active Ni-SI a states of [NiFe] hydrogenase studied by utilizing Ni-SI r-to-Ni-SI a photoactivation. Chem Commun (Camb) 2018; 53:10444-10447. [PMID: 28884761 DOI: 10.1039/c7cc06061k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previously, the Ni-SIr state of [NiFe] hydrogenase was found to convert to the Ni-SIa state by light irradiation. Herein, large activation energies and a large kinetic isotope effect were obtained for the reconversion of the Ni-SIa state to the Ni-SIr state after the Ni-SIr-to-Ni-SIa photoactivation, suggesting that the Ni-SIa state reacts with H2O and leaves a bridging hydroxo ligand for the Ni-SIr state.
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Affiliation(s)
- Hulin Tai
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192, Japan. and CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Liyang Xu
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192, Japan.
| | - Koji Nishikawa
- Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Yoshiki Higuchi
- CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan and Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Shun Hirota
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192, Japan. and CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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4
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Krämer T, Kampa M, Lubitz W, van Gastel M, Neese F. Theoretical Spectroscopy of the NiIIIntermediate States in the Catalytic Cycle and the Activation of [NiFe] Hydrogenases. Chembiochem 2013; 14:1898-905. [DOI: 10.1002/cbic.201300104] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Indexed: 11/05/2022]
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5
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Bolligarla R, Das SK. Sulfur Oxygenation of [Ni(btdt)
2
]
2–
by Aerial Oxidation under Ambient Conditions – Syntheses, Crystal Structures, and Properties of [Bu
4
N]
2
[Ni(btdt)
2
] and [Bu
4
N]
2
[Ni(btdtO
2
)
2
]·H
2
O ({btdt}
2–
= 2,1,3‐Benzenethiadiazole‐5,6‐dithiolate). Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201101426] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Ramababu Bolligarla
- School of Chemistry, University of Hyderabad, P. O. Central University, Hyderabad 500046, Andhra Pradesh, India, Fax: +91‐40‐2301‐2460
| | - Samar K. Das
- School of Chemistry, University of Hyderabad, P. O. Central University, Hyderabad 500046, Andhra Pradesh, India, Fax: +91‐40‐2301‐2460
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6
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Horch M, Lauterbach L, Lenz O, Hildebrandt P, Zebger I. NAD(H)-coupled hydrogen cycling - structure-function relationships of bidirectional [NiFe] hydrogenases. FEBS Lett 2011; 586:545-56. [PMID: 22056977 DOI: 10.1016/j.febslet.2011.10.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 10/05/2011] [Accepted: 10/06/2011] [Indexed: 10/15/2022]
Abstract
Hydrogenases catalyze the activation or production of molecular hydrogen. Due to their potential importance for future biotechnological applications, these enzymes have been in the focus of intense research for the past decades. Bidirectional [NiFe] hydrogenases are of particular interest as they couple the reversible cleavage of hydrogen to the redox conversion of NAD(H). In this account, we review the current state of knowledge about mechanistic aspects and structural determinants of these complex multi-cofactor enzymes. Special emphasis is laid on the oxygen-tolerant NAD(H)-linked bidirectional [NiFe] hydrogenase from Ralstonia eutropha.
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Affiliation(s)
- M Horch
- Technische Universität Berlin, Institut für Chemie, Sekr. PC 14, Straße des 17. Juni 135, D-10623 Berlin, Germany
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7
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Ogata H, Kellers P, Lubitz W. The crystal structure of the [NiFe] hydrogenase from the photosynthetic bacterium Allochromatium vinosum: characterization of the oxidized enzyme (Ni-A state). J Mol Biol 2010; 402:428-44. [PMID: 20673834 DOI: 10.1016/j.jmb.2010.07.041] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 07/19/2010] [Accepted: 07/20/2010] [Indexed: 11/18/2022]
Abstract
The crystal structure of the membrane-associated [NiFe] hydrogenase from Allochromatium vinosum has been determined to 2.1 Å resolution. Electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopy on dissolved crystals showed that it is present in the Ni-A state (>90%). The structure of the A. vinosum [NiFe] hydrogenase shows significant similarities with [NiFe] hydrogenase structures derived from Desulfovibrio species. The amino acid sequence identity is ∼ 50%. The bimetallic [NiFe] active site is located in the large subunit of the heterodimer and possesses three diatomic non-protein ligands coordinated to the Fe (two CN(-) , one CO). Ni is bound to the protein backbone via four cysteine thiolates; two of them also bridge the two metals. One of the bridging cysteines (Cys64) exhibits a modified thiolate in part of the sample. A mono-oxo bridging ligand was assigned between the metal ions of the catalytic center. This is in contrast to a proposal for Desulfovibrio sp. hydrogenases that show a di-oxo species in this position for the Ni-A state. The additional metal site located in the large subunit appears to be a Mg(2+) ion. Three iron-sulfur clusters were found in the small subunit that forms the electron transfer chain connecting the catalytic site with the molecular surface. The calculated anomalous Fourier map indicates a distorted proximal iron-sulfur cluster in part of the crystals. This altered proximal cluster is supposed to be paramagnetic and is exchange coupled to the Ni(3+) ion and the medial [Fe(3)S(4)](+) cluster that are both EPR active (S=1/2 species). This finding of a modified proximal cluster in the [NiFe] hydrogenase might explain the observation of split EPR signals that are occasionally detected in the oxidized state of membrane-bound [NiFe] hydrogenases as from A. vinosum.
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Affiliation(s)
- Hideaki Ogata
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
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8
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Lenz O, Ludwig M, Schubert T, Bürstel I, Ganskow S, Goris T, Schwarze A, Friedrich B. H2 conversion in the presence of O2 as performed by the membrane-bound [NiFe]-hydrogenase of Ralstonia eutropha. Chemphyschem 2010; 11:1107-19. [PMID: 20186906 DOI: 10.1002/cphc.200901002] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
[NiFe]-hydrogenases catalyze the oxidation of H(2) to protons and electrons. This reversible reaction is based on a complex interplay of metal cofactors including the Ni-Fe active site and several [Fe-S] clusters. H(2) catalysis of most [NiFe]-hydrogenases is sensitive to dioxygen. However, some bacteria contain hydrogenases that activate H(2) even in the presence of O(2). There is now compelling evidence that O(2) affects hydrogenase on three levels: 1) H(2) catalysis, 2) hydrogenase maturation, and 3) H(2)-mediated signal transduction. Herein, we summarize the genetic, biochemical, electrochemical, and spectroscopic properties related to the O(2) tolerance of hydrogenases resident in the facultative chemolithoautotroph Ralstonia eutropha H16. A focus is given to the membrane-bound [NiFe]-hydogenase, which currently represents the best-characterized member of O(2)-tolerant hydrogenases.
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Affiliation(s)
- Oliver Lenz
- Department of Microbiology, Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany.
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9
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Fourmond V, Infossi P, Giudici-Orticoni MT, Bertrand P, Léger C. “Two-Step” Chronoamperometric Method for Studying the Anaerobic Inactivation of an Oxygen Tolerant NiFe Hydrogenase. J Am Chem Soc 2010; 132:4848-57. [DOI: 10.1021/ja910685j] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, UPR 9036, Institut de Biologie de la Méditerranée and Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Pascale Infossi
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, UPR 9036, Institut de Biologie de la Méditerranée and Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Marie-Thérèse Giudici-Orticoni
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, UPR 9036, Institut de Biologie de la Méditerranée and Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Patrick Bertrand
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, UPR 9036, Institut de Biologie de la Méditerranée and Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
| | - Christophe Léger
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, UPR 9036, Institut de Biologie de la Méditerranée and Aix-Marseille Université, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France
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10
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Pandelia ME, Ogata H, Currell LJ, Flores M, Lubitz W. Inhibition of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F by carbon monoxide: An FTIR and EPR spectroscopic study. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2010; 1797:304-13. [DOI: 10.1016/j.bbabio.2009.11.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 10/21/2009] [Accepted: 11/10/2009] [Indexed: 11/15/2022]
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11
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Millo D, Pandelia ME, Utesch T, Wisitruangsakul N, Mroginski MA, Lubitz W, Hildebrandt P, Zebger I. Spectroelectrochemical Study of the [NiFe] Hydrogenase from Desulfovibrio vulgaris Miyazaki F in Solution and Immobilized on Biocompatible Gold Surfaces. J Phys Chem B 2009; 113:15344-51. [DOI: 10.1021/jp906575r] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Diego Millo
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Maria-Eirini Pandelia
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Tillmann Utesch
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Nattawadee Wisitruangsakul
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Maria A. Mroginski
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Wolfgang Lubitz
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
| | - Ingo Zebger
- Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, Sekr. PC14, D-10623 Berlin, Germany, and Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34−36, D-45470 Mülheim/Ruhr, Germany
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12
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Germer F, Zebger I, Saggu M, Lendzian F, Schulz R, Appel J. Overexpression, isolation, and spectroscopic characterization of the bidirectional [NiFe] hydrogenase from Synechocystis sp. PCC 6803. J Biol Chem 2009; 284:36462-36472. [PMID: 19801638 DOI: 10.1074/jbc.m109.028795] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bidirectional [NiFe] hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 was purified to apparent homogeneity by a single affinity chromatography step using a Synechocystis mutant with a Strep-tag II fused to the C terminus of HoxF. To increase the yield of purified enzyme and to test its overexpression capacity in Synechocystis the psbAII promoter was inserted upstream of the hoxE gene. In addition, the accessory genes (hypF, C, D, E, A, and B) from Nostoc sp. PCC 7120 were expressed under control of the psbAII promoter. The respective strains show higher hydrogenase activities compared with the wild type. For the first time a Fourier transform infrared (FTIR) spectroscopic characterization of a [NiFe] hydrogenase from an oxygenic phototroph is presented, revealing that two cyanides and one carbon monoxide coordinate the iron of the active site. At least four different redox states of the active site were detected during the reversible activation/inactivation. Although these states appear similar to those observed in standard [NiFe] hydrogenases, no paramagnetic nickel state could be detected in the fully oxidized and reduced forms. Electron paramagnetic resonance spectroscopy confirms the presence of several iron-sulfur clusters after reductive activation. One [4Fe4S](+) and at least one [2Fe2S](+) cluster could be identified. Catalytic amounts of NADH or NADPH are sufficient to activate the reaction of this enzyme with hydrogen.
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Affiliation(s)
- Frauke Germer
- Botanisches Institut, Universität Kiel, Am Botanischen Garten 1-9, D-24118 Kiel, Germany
| | - Ingo Zebger
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17, Juni 135, D-10623 Berlin, Germany
| | - Miguel Saggu
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17, Juni 135, D-10623 Berlin, Germany
| | - Friedhelm Lendzian
- Max-Volmer-Laboratorium, Technische Universität Berlin, Strasse des 17, Juni 135, D-10623 Berlin, Germany
| | - Rüdiger Schulz
- Botanisches Institut, Universität Kiel, Am Botanischen Garten 1-9, D-24118 Kiel, Germany
| | - Jens Appel
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287.
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13
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Liu T, Li B, Singleton ML, Hall MB, Darensbourg MY. Sulfur oxygenates of biomimetics of the diiron subsite of the [FeFe]-hydrogenase active site: properties and oxygen damage repair possibilities. J Am Chem Soc 2009; 131:8296-307. [PMID: 19507910 DOI: 10.1021/ja9016528] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study explores the site specificity (sulfur vs the Fe-Fe bond) of oxygenation of diiron (Fe(I)Fe(I) and Fe(II)Fe(II)) organometallics that model the 2-iron subsite in the active site of [FeFe]-hydrogenase: (mu-pdt)[Fe(CO)(2)L][Fe(CO)(2)L'] (L = L' = CO (1); L = PPh(3), L' = CO (2); L = L' = PMe(3) (4)) and (mu-pdt)(mu-H)[Fe(CO)(2)PMe(3)](2) (5). DFT computations find that the Fe-Fe bond in the Fe(I)Fe(I) diiron models is thermodynamically favored to produce the mu-oxo or oxidative addition product, Fe(II)-O-Fe(II); nevertheless, the sulfur-based HOMO-1 accounts for the experimentally observed mono- and bis-O-atom adducts at sulfur, i.e., (mu-pst)[Fe(CO)(2)L][Fe(CO)(2)L'] (pst = -S(CH(2))(3)S(O)-, 1,3-propanesulfenatothiolate; L = L' = CO (1-O); L = PPh(3), L' = CO (2-O); L = L' = PMe(3) (4-O)) and (mu-pds)[Fe(CO)(2)L][Fe(CO)(2)L'] (pds = -(O)S(CH(2))(3)S(O)-, 1,3-propanedisulfenato; L = PPh(3), L' = CO (2-O(2))). The Fe(II)(mu-H)Fe(II) diiron model (5), for which the HOMO is largely of sulfur character, exclusively yields S-oxygenation. The depressing effect of such bridging ligand modification on the dynamic NMR properties arising from rotation of the Fe(CO)(3) correlates with higher barriers to the CO/PMe(3) exchange of (mu-pst)[Fe(CO)(3)](2) as compared to (mu-pdt)[Fe(CO)(3)](2). Five molecular structures are confirmed by X-ray diffraction: 1-O, 2-O, 2-O(2), 4-O, and 6. Deoxygenation with reclamation of the mu-pdt parent complex occurs in a proton/electron-coupled process. The possible biological relevance of oxygenation and deoxygenation studies is discussed.
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Affiliation(s)
- Tianbiao Liu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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14
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Saggu M, Zebger I, Ludwig M, Lenz O, Friedrich B, Hildebrandt P, Lendzian F. Spectroscopic insights into the oxygen-tolerant membrane-associated [NiFe] hydrogenase of Ralstonia eutropha H16. J Biol Chem 2009; 284:16264-16276. [PMID: 19304663 DOI: 10.1074/jbc.m805690200] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
This study provides the first spectroscopic characterization of the membrane-bound oxygen-tolerant [NiFe] hydrogenase (MBH) from Ralstonia eutropha H16 in its natural environment, the cytoplasmic membrane. The H2-converting MBH is composed of a large subunit, harboring the [NiFe] active site, and a small subunit, capable in coordinating one [3Fe4S] and two [4Fe4S] clusters. The hydrogenase dimer is electronically connected to a membrane-integral cytochrome b. EPR and Fourier transform infrared spectroscopy revealed a strong similarity of the MBH active site with known [NiFe] centers from strictly anaerobic hydrogenases. Most redox states characteristic for anaerobic [NiFe] hydrogenases were identified except for one remarkable difference. The formation of the oxygen-inhibited Niu-A state was never observed. Furthermore, EPR data showed the presence of an additional paramagnetic center at high redox potential (+290 mV), which couples magnetically to the [3Fe4S] center and indicates a structural and/or redox modification at or near the proximal [4Fe4S] cluster. Additionally, significant differences regarding the magnetic coupling between the Nia-C state and [4Fe4S] clusters were observed in the reduced form of the MBH. The spectroscopic properties are discussed with regard to the unusual oxygen tolerance of this hydrogenase and in comparison with those of the solubilized, dimeric form of the MBH.
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Affiliation(s)
- Miguel Saggu
- From the Institut für Chemie, Technische Universität Berlin, PC14, Strasse des 17. Juni 135, D-10623 Berlin
| | - Ingo Zebger
- From the Institut für Chemie, Technische Universität Berlin, PC14, Strasse des 17. Juni 135, D-10623 Berlin.
| | - Marcus Ludwig
- Institute of Biology, Department of Microbiology, Humboldt-Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
| | - Oliver Lenz
- Institute of Biology, Department of Microbiology, Humboldt-Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
| | - Bärbel Friedrich
- Institute of Biology, Department of Microbiology, Humboldt-Universität zu Berlin, Chausseestrasse 117, D-10115 Berlin, Germany
| | - Peter Hildebrandt
- From the Institut für Chemie, Technische Universität Berlin, PC14, Strasse des 17. Juni 135, D-10623 Berlin
| | - Friedhelm Lendzian
- From the Institut für Chemie, Technische Universität Berlin, PC14, Strasse des 17. Juni 135, D-10623 Berlin.
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15
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16
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Hoeben FJM, Meijer FS, Dekker C, Albracht SPJ, Heering HA, Lemay SG. Toward single-enzyme molecule electrochemistry: [NiFe]-hydrogenase protein film voltammetry at nanoelectrodes. ACS Nano 2008; 2:2497-2504. [PMID: 19206284 DOI: 10.1021/nn800518d] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have scaled down electrochemical assays of redox-active enzymes enabling us to study small numbers of molecules. Our approach is based on lithographically fabricated Au nanoelectrodes with dimensions down to ca. 70 x 70 nm(2). We first present a detailed characterization of the electrodes using a combination of scanning electron microscopy, cyclic voltammetry, and finite-element modeling. We then demonstrate the viability of the approach by focusing on the highly active [NiFe]-hydrogenase from Allochromatium vinosum immobilized on polymyxin-pretreated Au. Using this system, we successfully demonstrate a distinct catalytic response from less than 50 enzyme molecules. These results strongly suggest the feasibility of using bioelectrochemistry as a new tool for studying redox enzymes at the single-molecule level.
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Affiliation(s)
- Freek J M Hoeben
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, Delft, The Netherlands
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Kellers P, Ogata H, Lubitz W. Purification, crystallization and preliminary X-ray analysis of the membrane-bound [NiFe] hydrogenase from Allochromatium vinosum. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:719-22. [PMID: 18678940 PMCID: PMC2494966 DOI: 10.1107/s1744309108019945] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 06/30/2008] [Indexed: 11/11/2022]
Abstract
The membrane-bound [NiFe] hydrogenase is a unique metalloprotein that is able to catalyze the reversible oxidation of hydrogen to protons and electrons during a complex reaction cycle. The [NiFe] hydrogenase was isolated from the photosynthetic purple sulfur bacterium Allochromatium vinosum and its crystallization and preliminary X-ray analysis are reported. It was crystallized by the hanging-drop vapour-diffusion method using sodium citrate and imidazole as crystallization agents. The crystals belong to space group P2(1)2(1)2, with unit-cell parameters a = 205.00, b = 217.42, c = 120.44 A. X-ray diffraction data have been collected to 2.5 A resolution.
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Affiliation(s)
- Petra Kellers
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34–36, D-45470 Mülheim an der Ruhr, Germany
| | - Hideaki Ogata
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34–36, D-45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34–36, D-45470 Mülheim an der Ruhr, Germany
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18
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Hoeben FJM, Heller I, Albracht SPJ, Dekker C, Lemay SG, Heering HA. Polymyxin-coated Au and carbon nanotube electrodes for stable [NiFe]-hydrogenase film voltammetry. Langmuir 2008; 24:5925-5931. [PMID: 18459755 DOI: 10.1021/la703984z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report on the use of polymyxin (PM), a cyclic cationic lipodecapeptide, as an electrode modifier for studying protein film voltammetry (PFV) on Au and single-walled carbon nanotube (SWNT) electrodes. Pretreating the electrodes with PM allows for the subsequent immobilization of an active submonolayer of [NiFe]-hydrogenase from Allochromatium vinosum ( Av H2ase). Probed by cyclic voltammetry (CV), the adsorbed enzyme exhibits characteristic electrocatalytic behavior that is stable for several hours under continuous potential cycling. An unexpected feature of the immobilization procedure is that the presence of chloride ions is a prerequisite for obtaining electrocatalytic activity. Atomic force microscopy (AFM) relates the observed catalytic activity to enzymatic adsorption at the PM/Au(111) surface, and a combination of concentration-dependent CV and AFM is used to investigate the interaction between the enzyme and the PM layer.
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Affiliation(s)
- Freek J M Hoeben
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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Affiliation(s)
- Kylie A Vincent
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
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20
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Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
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Tsygankov AA, Minakov EA, Zorin NA, Gosteva KS, Voronin OG, Karyakin AA. Measuring the pH dependence of hydrogenase activities. Biochemistry Moscow 2007; 72:968-73. [PMID: 17922655 DOI: 10.1134/s0006297907090076] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- A A Tsygankov
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
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22
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De Lacey AL, Fernandez VM, Rousset M, Cammack R. Activation and Inactivation of Hydrogenase Function and the Catalytic Cycle: Spectroelectrochemical Studies. Chem Rev 2007; 107:4304-30. [PMID: 17715982 DOI: 10.1021/cr0501947] [Citation(s) in RCA: 405] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Antonio L De Lacey
- Instituto de CatAlisis, CSIC, Marie Curie 2, Cantoblanco, 28049 Madrid, Spain
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23
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Kolodziej AF. The Chemistry of Nickel-Containing Enzymes. In: Karlin KD, editor. Progress in Inorganic Chemistry. Hoboken: John Wiley & Sons, Inc.; 1994. pp. 493-597. [DOI: 10.1002/9780470166420.ch7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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Schröder O, Bleijlevens B, de Jongh TE, Chen Z, Li T, Fischer J, Förster J, Friedrich CG, Bagley KA, Albracht SPJ, Lubitz W. Characterization of a cyanobacterial-like uptake [NiFe] hydrogenase: EPR and FTIR spectroscopic studies of the enzyme from Acidithiobacillus ferrooxidans. J Biol Inorg Chem 2006; 12:212-33. [PMID: 17082918 DOI: 10.1007/s00775-006-0185-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Accepted: 09/27/2006] [Indexed: 10/24/2022]
Abstract
Electron paramagnetic resonance (EPR) and Fourier transform IR studies on the soluble hydrogenase from Acidithiobacillus ferrooxidans are presented. In addition, detailed sequence analyses of the two subunits of the enzyme have been performed. They show that the enzyme belongs to a group of uptake [NiFe] hydrogenases typical for Cyanobacteria. The sequences have also a close relationship to those of the H(2)-sensor proteins, but clearly differ from those of standard [NiFe] hydrogenases. It is concluded that the structure of the catalytic centre is similar, but not identical, to that of known [NiFe] hydrogenases. The active site in the majority of oxidized enzyme molecules, 97% in cells and more than 50% in the purified enzyme, is EPR-silent. Upon contact with H(2) these sites remain EPR-silent and show only a limited IR response. Oxidized enzyme molecules with an EPR-detectable active site show a Ni(r)*-like EPR signal which is light-sensitive at cryogenic temperatures. This is a novelty in the field of [NiFe] hydrogenases. Reaction with H(2) converts these active sites to the well-known Ni(a)-C* state. Illumination below 160 K transforms this state into the Ni(a)-L* state. The reversal, in the dark at 200 K, proceeds via an intermediate Ni EPR signal only observed with the H(2)-sensor protein from Ralstonia eutropha. The EPR-silent active sites in as-isolated and H(2)-treated enzyme are also light-sensitive as observed by IR spectra at cryogenic temperatures. The possible origin of the light sensitivity is discussed. This study represents the first spectral characterization of an enzyme of the group of cyanobacterial uptake hydrogenases.
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Affiliation(s)
- Olga Schröder
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, 10623, Berlin, Germany
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25
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Long M, Liu J, Chen Z, Bleijlevens B, Roseboom W, Albracht SPJ. Characterization of a HoxEFUYH type of [NiFe] hydrogenase from Allochromatium vinosum and some EPR and IR properties of the hydrogenase module. J Biol Inorg Chem 2006; 12:62-78. [PMID: 16969669 DOI: 10.1007/s00775-006-0162-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Accepted: 08/11/2006] [Indexed: 10/24/2022]
Abstract
A soluble hydrogenase from Allochromatium vinosum was purified. It consisted of a large (M (r) = 52 kDa) and a small (M (r) = 23 kDa) subunit. The genes encoding for both subunits were identified. They belong to an open reading frame where they are preceded by three more genes. A DNA fragment containing all five genes was cloned and sequenced. The deduced amino acid sequences of the products characterized the complex as a member of the HoxEFUYH type of [NiFe] hydrogenases. Detailed sequence analyses revealed binding sites for eight Fe-S clusters, three [2Fe-2S] clusters and five [4Fe-4S] clusters, six of which are also present in homologous subunits of [FeFe] hydrogenases and NADH:ubiquione oxidoreductases (complex I). This makes the HoxEFUYH type of hydrogenases the one that is evolutionary closest to complex I. The relative positions of six of the potential Fe-S clusters are predicted on the basis of the X-ray structures of the Clostridium pasteurianum [FeFe] hydrogenase I and the hydrophilic domain of complex I from Thermus thermophilus. Although the HoxF subunit contains binding sites for flavin mononucleotide and NAD(H), cell-free extracts of A. vinosum did not catalyse a H(2)-dependent reduction of NAD(+). Only the hydrogenase module (HoxYH) could be purified. Its electron paramagnetic resonance (EPR) and IR spectral properties showed the presence of a Ni-Fe active site and a [4Fe-4S] cluster. Its activity was sensitive to carbon monoxide. No EPR signals from a light-sensitive Ni(a)-C* state could be observed. This study presents the first IR spectroscopic data on the HoxYH module of a HoxEFUYH type of [NiFe] hydrogenase.
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Affiliation(s)
- Minnan Long
- School of Life Sciences, Bio-energy Center, Xiamen University, Xiamen, 361005, People's Republic of China.
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Pardo A, De Lacey AL, Fernández VM, Fan HJ, Fan Y, Hall MB. Density functional study of the catalytic cycle of nickel–iron [NiFe] hydrogenases and the involvement of high-spin nickel(II). J Biol Inorg Chem 2006; 11:286-306. [PMID: 16511689 DOI: 10.1007/s00775-005-0076-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Accepted: 12/14/2005] [Indexed: 10/25/2022]
Abstract
In light of recent experiments suggesting high-spin (HS) Ni(II) species in the catalytic cycle of [NiFe] hydrogenase, a series of models of the Ni(II) forms Ni-SI(I,II), SI-CO and Ni-R(I,II,III) were examined in their high-spin states via density functional calculations. Because of its importance in the catalytic cycle, the Ni-C form was also included in this study. Unlike the Ni(II) forms in previous studies, in which a low-spin (LS) state was assumed and a square-planar structure found, the optimized geometries of these HS Ni(II) forms resemble those observed in the crystal structures: a distorted tetrahedral to distorted pyramidal coordination for the NiS4. This resemblance is particularly significant because the LS state is 20-30 kcal/mol less stable than the HS state for the geometry of the crystal structure. If these Ni(II) forms in the enzyme are not high spin, a large change in geometry at the active site is required during the catalytic cycle. Furthermore, only the HS state for the CO-inhibited form SI-CO has CO stretching frequencies that match the experimental results. As in the previous work, these new results show that the heterolytic cleavage reaction of dihydrogen (where H2 is cleaved with the metal acting as a hydride acceptor and a cysteine as the proton acceptor) has a lower energy barrier and is more exothermic when the active site is oxidized to Ni(III). The enzyme models described here are supported by a calibrated correlation of the calculated and measured CO stretching frequencies of the forms of the enzyme. The correlation coefficient for the final set of models of the forms of [NiFe] hydrogenase is 0.8.
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Affiliation(s)
- Alejandro Pardo
- Instituto de Catalisis, CSIC, c/ Marie Curie s/n, Campus de Cantoblanco, 28049, Madrid, Spain
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27
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van der Linden E, Burgdorf T, de Lacey AL, Buhrke T, Scholte M, Fernandez VM, Friedrich B, Albracht SPJ. An improved purification procedure for the soluble [NiFe]-hydrogenase of Ralstonia eutropha: new insights into its (in)stability and spectroscopic properties. J Biol Inorg Chem 2006; 11:247-60. [PMID: 16418856 DOI: 10.1007/s00775-005-0075-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Accepted: 12/12/2005] [Indexed: 11/28/2022]
Abstract
Infrared (IR) spectra in combination with chemical analyses have recently shown that the active Ni-Fe site of the soluble NAD(+)-reducing [NiFe]-hydrogenase from Ralstonia eutropha contains four cyanide groups and one carbon monoxide as ligands. Experiments presented here confirm this result, but show that a variable percentage of enzyme molecules loses one or two of the cyanide ligands from the active site during routine purification. For this reason the redox conditions during the purification have been optimized yielding hexameric enzyme preparations (HoxFUYHI(2)) with aerobic specific H(2)-NAD(+) activities of 150-185 mumol/min/mg of protein (up to 200% of the highest activity previously reported in the literature). The preparations were highly homogeneous in terms of the active site composition and showed superior IR spectra. IR spectro-electrochemical studies were consistent with the hypothesis that only reoxidation of the reduced enzyme with dioxygen leads to the inactive state, where it is believed that a peroxide group is bound to nickel. Electron paramagnetic resonance experiments showed that the radical signal from the NADH-reduced enzyme derives from the semiquinone form of the flavin (FMN-a) in the hydrogenase module (HoxYH dimer), but not of the flavin (FMN-b) in the NADH-dehydrogenase module (HoxFU dimer). It is further demonstrated that the hexameric enzyme remains active in the presence of NADPH and air, whereas NADH and air lead to rapid destruction of enzyme activity. It is proposed that the presence of NADPH in cells keeps the enzyme in the active state.
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Affiliation(s)
- Eddy van der Linden
- Swammerdam Institute for Life Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
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28
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Jayapal P, Sundararajan M, Hillier IH, Burton NA. How are the ready and unready states of nickel–iron hydrogenase activated by H2? A density functional theory study. Phys Chem Chem Phys 2006; 8:4086-94. [PMID: 17028697 DOI: 10.1039/b608069c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have explored possible mechanisms for the formation of the catalytically active Ni(a)-S state of the enzyme, nickel iron hydrogenase, from the Ni*(r) (ready) or Ni*(u) (unready) state, by reaction with H(2), using density functional theory calculations with the BP86 functional in conjunction with a DZVP basis set. We find that for the reaction of the ready state, which is taken to have an -OH bridge, the rate determining step is the cleavage of H(2) at the Ni(3+) centre with a barrier of approximately 15 kcal mol(-1). We take the unready state to have a -OOH bridge, and find that reaction with H(2) to form the Ni(r)-S state can proceed by two possible routes. One such path has a number of steps involving electron transfer, which is consistent with experiment, as is the calculated barrier of approximately 19 kcal mol(-1). The alternative pathway, with a lower barrier, may not be rate determining. Overall, our predictions give barriers in line with experiment, and allow details of the mechanism to be explored which are inaccessible from experiment.
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Affiliation(s)
- Prabha Jayapal
- School of Chemistry, University of Manchester, Manchester, UK M13 9PL
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29
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Albracht SPJ, Roseboom W, Hatchikian EC. The active site of the [FeFe]-hydrogenase from Desulfovibrio desulfuricans. I. Light sensitivity and magnetic hyperfine interactions as observed by electron paramagnetic resonance. J Biol Inorg Chem 2005; 11:88-101. [PMID: 16323020 DOI: 10.1007/s00775-005-0039-8] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Accepted: 09/26/2005] [Indexed: 10/25/2022]
Abstract
The hydrogen-activating cluster (H cluster) in [FeFe]-hydrogenases consists of two moieties. The [2Fe]H subcluster is a (L)(CO)(CN)Fe(mu-RS2)(mu-CO)Fe(CysS)(CO)(CN) centre. The Cys-bound Fe is called Fe1, the other iron Fe2. The Cys-thiol forms a bridge to a [4Fe-4S] cluster, the [4Fe-4S]H subcluster. We report that electron paramagnetic resonance (EPR) spectra of the 57Fe-enriched enzyme from Desulfovibrio desulfuricans in the H(ox)-CO state are consistent with a magnetic hyperfine interaction of the unpaired spin with all six Fe atoms of the H cluster. In contrast to the inactive aerobic enzyme, the active enzyme is easily destroyed by light. The [2Fe]H subcluster in some enzyme molecules loses CO by photolysis, whereupon other molecules firmly bind the released CO to form the H(ox)-CO state giving rise to the so-called axial 2.06 EPR signal. Though not destroyed by light, the H(ox)-CO state is affected by it. As demonstrated in the accompanying paper [49] two of the intrinsic COs, both bound to Fe2, can be exchanged by extrinsic 13CO during illumination at 2 degrees C. We found that only one of the three 13COs, the one at the extrinsic position, gives an EPR-detectable isotropic superhyperfine interaction of 0.6 mT. At 30 K both the inhibiting extrinsic CO bound to Fe2 and one more CO can be photolysed. EPR spectra of the photolysed products are consistent with a 3d7 system of Fe with the formal oxidation state +1. The damaged enzyme shows a light-sensitive g = 5 signal which is ascribed to an S = 3/2 form of the [2Fe](H) subcluster. The light sensitivity of the enzyme explains the occurrence of the g = 5 signal and the axial 2.06 signal in published EPR spectra of nearly all preparations studied thus far.
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Affiliation(s)
- Simon P J Albracht
- Swammerdam Institute for Life Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV, Amsterdam, The Netherlands,
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Armstrong FA, Albracht SPJ. [NiFe]-hydrogenases: spectroscopic and electrochemical definition of reactions and intermediates. Philos Trans A Math Phys Eng Sci 2005; 363:937-54; discussion 1035-40. [PMID: 15991402 DOI: 10.1098/rsta.2004.1528] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Production and usage of di-hydrogen, H2, in micro-organisms is catalysed by highly active, 'ancient' metalloenzymes known as hydrogenases. Based on the number and identity of metal atoms in their active sites, hydrogenases fall into three main classes, [NiFe]-, [FeFe]- and [Fe]-. All contain the unusual ligand CO (and in most cases CN- as well) making them intriguing examples of 'organometallic' cofactors. These ligands render the active sites superbly 'visible' using infrared spectroscopy, which complements the use of electron paramagnetic resonance spectroscopy in studying mechanisms and identifying intermediates. Hydrogenases are becoming a focus of attention for research into future energy technologies, not only H2 production but also H2 oxidation in fuel cells. Hydrogenases immobilized on electrodes exhibit high electrocatalytic activity, providing not only an important new technique for their investigation, but also a basis for novel fuel cells either using the enzyme itself, or inspired synthetic catalysts. Favourable comparisons have been made with platinum electrocatalysts, an advantage of enzymes being their specificity for H2 and tolerance of CO. A challenge for exploiting hydrogenases is their sensitivity to O2, but some organisms are known to produce enzymes that overcome this problem by subtle alterations of the active site and gas access channels.
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Affiliation(s)
- Fraser A Armstrong
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, UK.
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31
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Roseboom W, Blokesch M, Böck A, Albracht SPJ. The biosynthetic routes for carbon monoxide and cyanide in the Ni-Fe active site of hydrogenases are different. FEBS Lett 2005; 579:469-72. [PMID: 15642360 DOI: 10.1016/j.febslet.2004.12.013] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 12/02/2004] [Accepted: 12/04/2004] [Indexed: 11/24/2022]
Abstract
The incorporation of carbon into the carbon monoxide and cyanide ligands of [NiFe]-hydrogenases has been investigated by using (13)C labelling in infrared studies of the Allochromatium vinosum enzyme and by (14)C labelling experiments with overproduced Hyp proteins from Escherichia coli. The results suggest that the biosynthetic routes of the carbon monoxide and cyanide ligands in [NiFe]-hydrogenases are different.
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Affiliation(s)
- Winfried Roseboom
- Swammerdam Institute for Life Sciences, University of Amsterdam, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, The Netherlands
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32
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Vincent KA, Cracknell JA, Parkin A, Armstrong FA. Hydrogen cycling by enzymes: electrocatalysis and implications for future energy technology. Dalton Trans 2005:3397-403. [PMID: 16234917 DOI: 10.1039/b508520a] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogenases provide an inspiration for future energy technologies. The active sites of these microbial enzymes contain Fe or Ni and Fe coordinated by CO and CN ligands: yet they have activities for hydrogen cycling that compare with Pt catalysts. Is there a future for enzymes in technological H2 cycling? There are obviously going to be disadvantages, perhaps overwhelming, as enzymes are notoriously fragile; yet what are the positive aspects and can we learn any chemistry that might be applied to produce the electrolytic and fuel cell catalysts of the future? We have developed a suite of novel electrochemical experiments to probe the chemistry of hydrogenases. The reactions are controlled and monitored at the surface of a small electrode, and characteristic catalytic properties are discernible from tiny amounts of sample material, so this approach can be used to search the microbial world for the best catalysts. Although electrochemistry does not provide structural information directly, it does give a "road map" by which to navigate the pathways and conditions that lead to particular states of the enzymes. This has prompted many interdisciplinary collaborations with other scientists who have provided microbiological, spectroscopic and structural contexts for this work. This article describes how these electrochemical experiments are set up, the data are analysed, and the results interpreted. We have determined mechanisms of catalysis, electron transfer, activation and inactivation, and defined important properties such as O2 tolerance and CO resistance in physical terms. Using an O2-tolerant hydrogenase, we have demonstrated a "proof of concept" miniature fuel cell that will run on a mixed H2/O2 feed in aqueous solution.
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Affiliation(s)
- Kylie A Vincent
- Department of Chemistry, Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford, UK OX1 3QR
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33
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De Lacey AL, Pardo A, Fernández VM, Dementin S, Adryanczyk-Perrier G, Hatchikian EC, Rousset M. FTIR spectroelectrochemical study of the activation and inactivation processes of [NiFe] hydrogenases: effects of solvent isotope replacement and site-directed mutagenesis. J Biol Inorg Chem 2004; 9:636-42. [PMID: 15175937 DOI: 10.1007/s00775-004-0559-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2004] [Accepted: 05/11/2004] [Indexed: 10/26/2022]
Abstract
The kinetics of the activation and anaerobic inactivation processes of Desulfovibrio gigas hydrogenase have been measured in D(2)O by FTIR spectroelectrochemistry. A primary kinetic solvent isotope effect was observed for the inactivation process but not for the activation step. The kinetics of these processes have been also measured after replacement of a glutamic residue placed near the active site of an analogous [NiFe] hydrogenase from Desulfovibrio fructosovorans. Its replacement by a glutamine affected greatly the kinetics of the inactivation process but only slightly the activation process. The interpretation of the experimental results is that the rate-limiting step for anaerobic inactivation is the formation from water of a micro-OH(-) bridge at the hydrogenase active site, and that Glu25 has a role in this step.
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Affiliation(s)
- Antonio L De Lacey
- Instituto de Catálisis, CSIC, Campus de Cantoblanco, 28049 Madrid, Spain.
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34
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Van der Linden E, Burgdorf T, Bernhard M, Bleijlevens B, Friedrich B, Albracht SPJ. The soluble [NiFe]-hydrogenase from Ralstonia eutropha contains four cyanides in its active site, one of which is responsible for the insensitivity towards oxygen. J Biol Inorg Chem 2004; 9:616-26. [PMID: 15164270 DOI: 10.1007/s00775-004-0555-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Accepted: 04/27/2004] [Indexed: 11/30/2022]
Abstract
Infrared spectra of (15)N-enriched preparations of the soluble cytoplasmic NAD(+)-reducing [NiFe]-hydrogenase from Ralstonia eutropha are presented. These spectra, together with chemical analyses, show that the Ni-Fe active site contains four cyanide groups and one carbon monoxide molecule. It is proposed that the active site is a (RS)(2)(CN)Ni(micro-RS)(2)Fe(CN)(3)(CO) centre (R=Cys) and that H(2) activation solely takes place on nickel. One of the two FMN groups (FMN-a) in the enzyme can be reversibly released upon reduction of the enzyme. It is now reported that at longer times also one of the cyanide groups, the one proposed to be bound to the nickel atom, could be removed from the enzyme. This process was irreversible and induced the inhibition of the enzyme activity by oxygen; the enzyme remained insensitive to carbon monoxide. The Ni-Fe active site was EPR undetectable under all conditions tested. It is concluded that the Ni-bound cyanide group is responsible for the oxygen insensitivity of the enzyme.
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Affiliation(s)
- Eddy Van der Linden
- Swammerdam Institute for Life Sciences, Biochemistry, University of Amsterdam, Plantage Muidergracht 12, 1018 TV Amsterdam, The Netherlands
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35
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36
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Lamle SE, Vincent KA, Halliwell LM, Albracht SPJ, Armstrong FA. Hydrogenase on an electrode: a remarkable heterogeneous catalyst. Dalton Trans 2003. [DOI: 10.1039/b306234c] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kurkin S, Meuer J, Koch J, Hedderich R, Albracht SPJ. The membrane-bound [NiFe]-hydrogenase (Ech) from Methanosarcina barkeri: unusual properties of the iron-sulphur clusters. Eur J Biochem 2002; 269:6101-11. [PMID: 12473105 DOI: 10.1046/j.1432-1033.2002.03328.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The purified membrane-bound [NiFe]-hydrogenase from Methanosarcina barkeri was studied with electron paramagnetic resonance (EPR) focusing on the properties of the iron-sulphur clusters. The EPR spectra showed signals from three different [4Fe-4S] clusters. Two of the clusters could be reduced under 101 kPa of H2, whereas the third cluster was only partially reduced. Magnetic interaction of one of the clusters with an unpaired electron localized on the Ni-Fe site indicated that this was the proximal cluster as found in all [NiFe]-hydrogenases. Hence, this cluster was assigned to be located in the EchC subunit. The other two clusters could therefore be assigned to be bound to the EchF subunit, which has two conserved four-Cys motifs for the binding of a [4Fe-4S] cluster. Redox titrations at different pH values demonstrated that the proximal cluster and one of the clusters in the EchF subunit had a pH-dependent midpoint potential. The possible relevance of these properties for the function of this proton-pumping [NiFe]-hydrogenase is discussed.
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Affiliation(s)
- Sergei Kurkin
- Swammerdam Institute for Life Sciences, Biochemistry, University of Amsterdam, the Netherlands; Max-Planck-Institut für Terrestrische Mikrobiologie, Marburg, Germany
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Happe RP, Roseboom W, Egert G, Friedrich CG, Massanz C, Friedrich B, Albracht SP. Unusual FTIR and EPR properties of the H2-activating site of the cytoplasmic NAD-reducing hydrogenase from Ralstonia eutropha. FEBS Lett 2000; 466:259-63. [PMID: 10682839 DOI: 10.1016/s0014-5793(99)01799-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Soluble NAD-reducing [NiFe]-hydrogenase (SH) from Ralstonia eutropha (formerly Alcaligenes eutrophus) has an infrared spectrum with one strong band at 1956 cm(-1) and four weak bands at 2098, 2088, 2081 and 2071 cm(-1) in the 2150-1850 cm(-1) spectral region. Other [NiFe]-hydrogenases only show one strong and two weak bands in this region, attributable to the NiFe(CN)2(CO) active site. The position of these three bands is highly sensitive to redox changes of the active site. In contrast, reduction of the SH resulted in a shift to lower frequencies of the 2098 cm(-1) band only. These and other properties prompted us to propose the presence of a Ni(CN)Fe(CN)3(CO) active site.
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Affiliation(s)
- R P Happe
- E.C. Slater Institute, Biochemistry, University of Amsterdam, Plantage Muidergracht, The Netherlands
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39
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Pierik AJ, Roseboom W, Happe RP, Bagley KA, Albracht SP. Carbon monoxide and cyanide as intrinsic ligands to iron in the active site of [NiFe]-hydrogenases. NiFe(CN)2CO, Biology's way to activate H2. J Biol Chem 1999; 274:3331-7. [PMID: 9920874 DOI: 10.1074/jbc.274.6.3331] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Infrared-spectroscopic studies on the [NiFe]-hydrogenase of Chromatium vinosum-enriched in 15N or 13C, as well as chemical analyses, show that this enzyme contains three non-exchangeable, intrinsic, diatomic molecules as ligands to the active site, one carbon monoxide molecule and two cyanide groups. The results form an explanation for the three non-protein ligands to iron detected in the crystal structure of the Desulfovibrio gigas hydrogenase (Volbeda, A., Garcin, E., Piras, C., De Lacey, A. I., Fernandez, V. M., Hatchikian, E. C., Frey, M., and Fontecilla-Camps, J. C. (1996) J. Am. Chem. Soc. 118, 12989-12996) and for the low spin character of the lone ferrous iron ion observed with Mössbauer spectroscopy (Surerus, K. K., Chen, M., Van der Zwaan, W., Rusnak, F. M., Kolk, M. , Duin, E. C., Albracht, S. P. J., and Münck, E. (1994) Biochemistry 33, 4980-4993). The results do not support the notion, based upon studies of Desulfovibrio vulgaris [NiFe]-hydrogenase (Higuchi, Y., Yagi, T., and Noritake, Y. (1997) Structure 5, 1671-1680), that SO is a ligand to the active site. The occurrence of both cyanide and carbon monoxide as intrinsic constituents of a prosthetic group is unprecedented in biology.
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Affiliation(s)
- A J Pierik
- E. C. Slater Institute, Biochemistry, University of Amsterdam, Plantage Muidergracht 12, NL-1018 TV Amsterdam, The Netherlands
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Happe RP, Roseboom W, Albracht SP. Pre-steady-state kinetics of the reactions of [NiFe]-hydrogenase from Chromatium vinosum with H2 and CO. Eur J Biochem 1999; 259:602-8. [PMID: 10092843 DOI: 10.1046/j.1432-1327.1999.00057.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Results are presented of the first rapid-mixing/rapid-freezing studies with a [NiFe]-hydrogenase. The enzyme from Chromatium vinosum was used. In particular the reactions of active enzyme with H2 and CO were monitored. The conversion from fully reduced, active hydrogenase (Nia-SR state) to the Nia-C* state was completed in less than 8 ms, a rate consistent with the H2-evolution activity of the enzyme. The reaction of CO with fully reduced enzyme was followed from 8 to 200 ms. The Nia-SR state did not react with CO. It was discovered, contrary to expectations, that the Nia-C* state did not react with CO when reactions were performed in the dark. When H2 was replaced by CO, a Nia-C* EPR signal appeared within 11 ms; this was also the case when H2 was replaced by Ar. With CO, however, the Nia-C* state decayed within 40 ms, due to the generation of the Nia-S.CO state (the EPR-silent state of the enzyme with bound CO). The Nia-C* state, induced after 11 ms by replacing H2 by CO in the dark, could be converted, in the frozen enzyme, into the EPR-detectable state with CO bound to nickel (Nia*.CO) by illumination at 30 K (evoking the Nia-L* state), followed by dark adaptation at 200 K. This can be explained by assuming that the Nia-C* state represents a formally trivalent state of nickel, which is unable to bind CO, whereas nickel in the Nia-L* and the Nia*.CO states is formally monovalent.
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Affiliation(s)
- R P Happe
- E.C. Slater Institute, University of Amsterdam, The Netherlands
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41
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Abstract
A third hydrogenase was recently identified in the proteobacterium Alcaligenes eutrophus as a constituent of a novel H2-sensing multicomponent regulatory system. This regulatory hydrogenase (RH) has been overexpressed in cells deficient in both the NAD+-reducing [NiFe]-hydrogenase and the membrane-bound [NiFe]-hydrogenase. EPR, FTIR and activity studies of membrane-free extracts revealed that the RH has an active site much like that of standard [NiFe]-hydrogenases, i.e. a Ni-Fe site with two CN- groups and one CO molecule. Its catalytic power is low, but the RH is always active, insensitive to oxygen, and occurs in only two redox states.
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Affiliation(s)
- A J Pierik
- E.C. Slater Institute, Biochemistry, University of Amsterdam, The Netherlands
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Butt JN, Filipiak M, Hagen WR. Direct electrochemistry of Megasphaera elsdenii iron hydrogenase. Definition of the enzyme's catalytic operating potential and quantitation of the catalytic behaviour over a continuous potential range. Eur J Biochem 1997; 245:116-22. [PMID: 9128731 DOI: 10.1111/j.1432-1033.1997.00116.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The Fe-hydrogenase from Megasphaera elsdenii undergoes direct electron exchange with glassy carbon electrodes. Cyclic voltammetry defines the catalytic-performance of the enzyme over a continuous but precisely defined range of potentials. In the presence of H2 and protons the bias of the enzyme towards H2 production is readily visualised. Variation of the response with pH indicates that protein ionisations with pK of approximately 6.7 and 8.3 regulate the catalytic activity. Possible origins for these observations in the chemistry of the H2-activating site are discussed. The mid-wave potential of the catalytic response, Emid, is defined as the catalytic operating potential of the enzyme. Under an atmosphere of hydrogen Emid = -421 +/- 10 mV, pH 7 with a variation of -21 +/- 4 mV pH-1, 22 degrees C. Deviation of Emid from the thermodynamic potential of the hydrogen/proton couple reflects the enzyme's influence over the catalysed reaction. Emid is the reduction potential of the H2-activating centre (H-cluster) in the absence of kinetic bottle-necks at other steps in the reaction mechanism.
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Affiliation(s)
- J N Butt
- Department of Biochemistry, Agricultural University of Wageningen, The Netherlands
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van der Spek TM, Arendsen AF, Happe RP, Yun S, Bagley KA, Stufkens DJ, Hagen WR, Albracht SP. Similarities in the architecture of the active sites of Ni-hydrogenases and Fe-hydrogenases detected by means of infrared spectroscopy. Eur J Biochem 1996; 237:629-34. [PMID: 8647106 DOI: 10.1111/j.1432-1033.1996.0629p.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Three groups that absorb in the 2100-1800-cm-1 infrared spectral region have recently been detected in Ni-hydrogenase from Chromatium vinosum [Bagley, K.A., Duin, E.C., Roseboom, W., Albracht, S. P.J. & Woodruff, W.H. (1995) Biochemistry 34, 5527-5535]. To assess the significance and generality of this observation, we have carried out an infrared-spectroscopic study of eight hydrogenases of three different types (nickel, iron and metal-free) and of 11 other iron-sulfur and/or nickel proteins. Infrared bands in the 2100-1800-cm-1 spectral region were found in spectra of all Ni-hydrogenases and Fe-hydrogenases and were absent from spectra of any of the other proteins, including a metal-free hydrogenase. The positions of these bands are dependent on the redox state of the hydrogenase. The three groups in Ni-hydrogenases that are detected by infrared spectroscopy are assigned to the three unidentified small non-protein ligands that coordinate iron in the dinuclear Ni/Fe active site as observed in the X-ray structure of the enzyme from Desulfovibrio gigas [Volbeda, A., Charon, M.-H., Piras, C., Hatchikian, E.C., Frey, M. & Fontecilla-Camps, J.C. (1995) Nature 373, 580-587]. It is concluded that these groups occur exclusively in metal-containing H2-activating enzymes. It is proposed that the active sites of Ni-hydrogenases and of Fe-hydrogenases have a similar architecture, that is required for the activation of molecular hydrogen.
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Affiliation(s)
- T M van der Spek
- E. C. Slater Institute, BioCentrum Amsterdam, University of Amsterdam, The Netherlands
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Affiliation(s)
| | | | - Lloyd W. Sumner
- Department of Chemistry, Texas A & M University College Station, Texas 77843
| | - David H. Russell
- Department of Chemistry, Texas A & M University College Station, Texas 77843
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45
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Affiliation(s)
- S P Albracht
- E.C. Slater Institute, BioCentrum Amsterdam, University of Amsterdam, The Netherlands
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46
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Bagley KA, Van Garderen CJ, Chen M, Duin EC, Albracht SP, Woodruff WH. Infrared studies on the interaction of carbon monoxide with divalent nickel in hydrogenase from Chromatium vinosum. Biochemistry 1994; 33:9229-36. [PMID: 8049224 DOI: 10.1021/bi00197a026] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Infrared spectra of a carbon monoxy-bound form of the EPR silent Ni(II) species of hydrogenase isolated from Chromatium vinosum are presented. These spectra show a band at 2060 cm-1 due to v(CO) for a metal-CO complex. This absorbance shifts to 2017 cm-1 upon exposure of the enzyme to 13CO. This band is attributed to v(CO) from a Ni(II)-CO species. It is shown that the CO on this species is photolabile at cryogenic temperatures but rebinds to form the original carbon monoxy species at temperatures above 200 K. In addition to the v(CO) band, infrared lines are detected at 2082, 2069, and 1929 cm-1, which shift slightly higher in frequency upon photolysis of the CO from the Ni. These infrared bands do not arise from CO itself on the basis of the fact that the frequency of these bands is unaffected by exposure of the enzyme to 13CO. Experiments in D2O show that these bands do not arise from an exchangeable hydrogen species. It is concluded that these non-CO bands arise from species near or coordinated to the Ni active site. The possible nature of these bands is discussed.
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Affiliation(s)
- K A Bagley
- Isotope and Nuclear Chemistry Division, INC-14, C-345 Los Alamos National Laboratory, New Mexico 87545
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47
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Moreno C, Franco R, Moura I, Le Gall J, Moura JJ. Voltammetric studies of the catalytic electron-transfer process between the Desulfovibrio gigas hydrogenase and small proteins isolated from the same genus. Eur J Biochem 1993; 217:981-9. [PMID: 8223656 DOI: 10.1111/j.1432-1033.1993.tb18329.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The kinetics of electron transfer between the Desulfovibrio gigas hydrogenase and several electron-transfer proteins from Desulfovibrio species were investigated by cyclic voltammetry, square-wave voltammetry and chronoamperometry. The cytochrome c3 from Desulfovibrio vulgaris (Hildenborough), Desulfovibrio desulfuricans (Norway 4), Desulfovibrio desulfuricans (American Type Culture Collection 27774) and D. gigas (NCIB 9332) were used as redox carriers. They differ in their redox potentials and isoelectric point. Depending on the pH, all the reduced forms of these cytochromes were effective in electron exchange with hydrogenase. Other small electron-transfer proteins such as ferredoxin I, ferredoxin II and rubredoxin from D. gigas were tentatively used as redox carriers. Only ferredoxin II was effective in mediating electron exchange between hydrogenase and the working electrode. The second-order rate constants k for the reaction between reduced proteins and hydrogenase were calculated based on the theory of the simplest electrocatalytic mechanism [Moreno, C., Costa, C., Moura, I., Le Gall, J., Liu, M. Y., Payne, W. J., van Dijk, C. & Moura, J. J. G. (1993) Eur. J. Biochem. 212, 79-86] and the results obtained by cyclic voltammetry were compared with those obtained by chronoamperometry. Values for k of 10(5)-10(6) M-1 s-1 (cytochrome c3 as electron carrier) and 10(4) M-1 s-1 (ferredoxin II as the electron carrier) were determined. The rate-constant values are discussed in terms of the existence of an electrostatic interaction between the electrode surface and the redox carrier and between the redox carrier and a positively charged part of the enzyme.
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Affiliation(s)
- C Moreno
- Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal
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48
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Franco R, Moura I, LeGall J, Peck HD, Huynh BH, Moura JJ. Characterization of D. desulfuricans (ATCC 27774) [NiFe] hydrogenase EPR and redox properties of the native and the dihydrogen reacted states. Biochim Biophys Acta 1993; 1144:302-8. [PMID: 8399280 DOI: 10.1016/0005-2728(93)90115-v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Redox intermediates of D. desulfuricans ATCC 27774 [NiFe] hydrogenase were generated under dihydrogen. Detailed redox titrations, coupled to EPR measurements, give access to the mid-point redox potentials of the iron-sulfur centers and of the Nickel-B signal that represents the ready form of the enzyme. The interaction between the dihydrogen molecule and the nickel centre was probed by the observation of an isotopic effect on the EPR signals detected in turnover conditions, by comparison of the H2O/H2 and D2O/D2-reacted samples.
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Affiliation(s)
- R Franco
- Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Monte de Caparica, Portugal
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49
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Abstract
Redox titrations of the nickel ion in active hydrogenase from Methanobacterium thermoautotrophicum and Chromatium vinosum were performed in the absence of artificial redox mediators, by variation of the H2-partial pressure. These experiments revealed a redox behaviour of the nickel ion which differed remarkably from previous redox titrations in the presence of redox mediators. Notably the EPR signal of the species earlier characterized as monovalent nickel with bound hydrogen, behaved as an n = 2 redox component upon reduction under varying H2-partial pressures. The EPR signal was not a transient one and persisted upon removal of hydrogen. Possible redox processes to explain these observations are discussed. A similar behaviour of nickel was also observed in enzyme as present in intact cells of M. thermoautotrophicum. These results suggest that nickel hydrogenases possess a second site for reaction with H2.
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Affiliation(s)
- J M Coremans
- E.C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands
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