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Badiani VM, Cobb SJ, Wagner A, Oliveira AR, Zacarias S, Pereira IAC, Reisner E. Elucidating Film Loss and the Role of Hydrogen Bonding of Adsorbed Redox Enzymes by Electrochemical Quartz Crystal Microbalance Analysis. ACS Catal 2022; 12:1886-1897. [PMID: 35573129 PMCID: PMC9097293 DOI: 10.1021/acscatal.1c04317] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/13/2021] [Indexed: 12/17/2022]
Abstract
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The immobilization of redox enzymes
on electrodes enables the efficient
and selective electrocatalysis of useful reactions such as the reversible
interconversion of dihydrogen (H2) to protons (H+) and formate to carbon dioxide (CO2) with hydrogenase
(H2ase) and formate dehydrogenase (FDH), respectively.
However, their immobilization on electrodes to produce electroactive
protein films for direct electron transfer (DET) at the protein–electrode
interface is not well understood, and the reasons for their activity
loss remain vague, limiting their performance often to hour timescales.
Here, we report the immobilization of [NiFeSe]-H2ase and
[W]-FDH from Desulfovibrio vulgaris Hildenborough on a range of charged and neutral self-assembled monolayer
(SAM)-modified gold electrodes with varying hydrogen bond (H-bond)
donor capabilities. The key factors dominating the activity and stability
of the immobilized enzymes are determined using protein film voltammetry
(PFV), chronoamperometry (CA), and electrochemical quartz crystal
microbalance (E-QCM) analysis. Electrostatic and H-bonding interactions
are resolved, with electrostatic interactions responsible for enzyme
orientation while enzyme desorption is strongly limited when H-bonding
is present at the enzyme–electrode interface. Conversely, enzyme
stability is drastically reduced in the absence of H-bonding, and
desorptive enzyme loss is confirmed as the main reason for activity
decay by E-QCM during CA. This study provides insights into the possible
reasons for the reduced activity of immobilized redox enzymes and
the role of film loss, particularly H-bonding, in stabilizing bioelectrode
performance, promoting avenues for future improvements in bioelectrocatalysis.
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Affiliation(s)
- Vivek M. Badiani
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
- Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, U.K
| | - Samuel J. Cobb
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Andreas Wagner
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Ana Rita Oliveira
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Sónia Zacarias
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Inês A. C. Pereira
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Erwin Reisner
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
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A variety of hydrogenotrophic enrichment cultures catalyse cathodic reactions. Sci Rep 2019; 9:2356. [PMID: 30787309 PMCID: PMC6382808 DOI: 10.1038/s41598-018-38006-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/18/2018] [Indexed: 12/03/2022] Open
Abstract
Biocathodes where living microorganisms catalyse reduction of CO2 can potentially be used to produce valuable chemicals. Microorganisms harbouring hydrogenases may play a key role for biocathode performance since H2 generated on the electrode surface can act as an electron donor for CO2 reduction. In this study, the possibility of catalysing cathodic reactions by hydrogenotrophic methanogens, acetogens, sulfate-reducers, denitrifiers, and acetotrophic methanogens was investigated. The cultures were enriched from an activated sludge inoculum and performed the expected metabolic functions. All enrichments formed distinct microbial communities depending on their electron donor and electron acceptor. When the cultures were added to an electrochemical cell, linear sweep voltammograms showed a shift in current generation close to the hydrogen evolution potential (−1 V versus SHE) with higher cathodic current produced at a more positive potential. All enrichment cultures except the denitrifiers were also used to inoculate biocathodes of microbial electrolysis cells operated with H+ and bicarbonate as electron acceptors and this resulted in current densities between 0.1–1 A/m2. The microbial community composition of biocathodes inoculated with different enrichment cultures were as different from each other as they were different from their suspended culture inoculum. It was noteworthy that Methanobacterium sp. appeared on all the biocathodes suggesting that it is a key microorganism catalysing biocathode reactions.
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3
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Maiti BK, Almeida RM, Moura I, Moura JJ. Rubredoxins derivatives: Simple sulphur-rich coordination metal sites and its relevance for biology and chemistry. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2017.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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4
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Lojou E. Hydrogenases as catalysts for fuel cells: Strategies for efficient immobilization at electrode interfaces. Electrochim Acta 2011. [DOI: 10.1016/j.electacta.2011.03.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Rosenbaum M, Aulenta F, Villano M, Angenent LT. Cathodes as electron donors for microbial metabolism: which extracellular electron transfer mechanisms are involved? BIORESOURCE TECHNOLOGY 2011; 102:324-33. [PMID: 20688515 DOI: 10.1016/j.biortech.2010.07.008] [Citation(s) in RCA: 283] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 06/29/2010] [Accepted: 07/02/2010] [Indexed: 05/20/2023]
Abstract
This review illuminates extracellular electron transfer mechanisms that may be involved in microbial bioelectrochemical systems with biocathodes. Microbially-catalyzed cathodes are evolving for new bioprocessing applications for waste(water) treatment, carbon dioxide fixation, chemical product formation, or bioremediation. Extracellular electron transfer processes in biological anodes, were the electrode serves as electron acceptor, have been widely studied. However, for biological cathodes the question remains: what are the biochemical mechanisms for the extracellular electron transfer from a cathode (electron donor) to a microorganism? This question was approached by not only analysing the literature on biocathodes, but also by investigating known extracellular microbial oxidation reactions in environmental processes. Here, it is predicted that in direct electron transfer reactions, c-type cytochromes often together with hydrogenases play a critical role and that, in mediated electron transfer reactions, natural redox mediators, such as PQQ, will be involved in the bioelectrochemical reaction. These mechanisms are very similar to processes at the bioanode, but the components operate at different redox potentials. The biocatalyzed cathode reactions, thereby, are not necessarily energy conserving for the microorganism.
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Affiliation(s)
- Miriam Rosenbaum
- Department of Biological and Environmental Engineering, Cornell University, 214 Riley-Robb Hall, Ithaca, NY 14853, USA.
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6
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Hydrogenases from the hyperthermophilic bacterium Aquifex aeolicus: electrocatalysis of the hydrogen production/consumption reactions at carbon electrodes. J Electroanal Chem (Lausanne) 2005. [DOI: 10.1016/j.jelechem.2004.11.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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7
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Heering HA, Wiertz FGM, Dekker C, de Vries S. Direct Immobilization of Native Yeast Iso-1 Cytochrome c on Bare Gold: Fast Electron Relay to Redox Enzymes and Zeptomole Protein-Film Voltammetry. J Am Chem Soc 2004; 126:11103-12. [PMID: 15339197 DOI: 10.1021/ja046737w] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyclic voltammetry shows that yeast iso-1-cytochrome c (YCC), chemisorbed on a bare gold electrode via Cys102, exhibits fast, reversible interfacial electron transfer (k(0) = 1.8 x 10(3) s(-1)) and retains its native functionality. Vectorially immobilized YCC relays electrons to yeast cytochrome c peroxidase, and to both cytochrome cd(1) nitrite reductase (NIR) and nitric oxide reductase from Paracoccus denitrificans, thereby revealing the mechanistic properties of these enzymes. On a microelectrode, we measured nitrite turnover by approximately 80 zmol (49 000 molecules) of NIR, coadsorbed on 0.65 amol (390 000 molecules) of YCC.
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Affiliation(s)
- Hendrik A Heering
- Contribution from the Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
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8
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Jones AK, Lamle SE, Pershad HR, Vincent KA, Albracht SPJ, Armstrong FA. Enzyme electrokinetics: electrochemical studies of the anaerobic interconversions between active and inactive states of Allochromatium vinosum [NiFe]-hydrogenase. J Am Chem Soc 2003; 125:8505-14. [PMID: 12848556 DOI: 10.1021/ja035296y] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cycling between active and inactive states of the catalytic center of [NiFe]-hydrogenase from Allochromatium vinosum has been investigated by dynamic electrochemical techniques. Adsorbed on a rotating disk pyrolytic graphite "edge" electrode, the enzyme is highly electroactive: this allows precise manipulations of the complex redox chemistry and facilitates quantitative measurements of the interconversions between active catalytic states and the inactive oxidized form Ni(r) (also called Ni-B or "ready") as functions of pH, H(2) partial pressure, temperature, and electrode potential. Cyclic voltammograms for catalytic H(2) oxidation (current is directly related to turnover rate) are highly asymmetric (except at pH > 8 and high temperature) due to inactivation being much slower than activation. Controlled potential-step experiments show that the rate of oxidative inactivation increases at high pH but is independent of potential, whereas the rate of reductive activation increases as the potential becomes more negative. Indeed, at 45 degrees C, activation takes just a few seconds at -288 mV. The cyclic asymmetry arises because interconversion is a two-stage reaction, as expected if the reduced inactive Ni(r)-S state is an intermediate. The rate of inactivation depends on a chemical process (rearrangement and uptake of a ligand) that is independent of potential, but sensitive to pH, while activation is driven by an electron-transfer process, Ni(III) to Ni(II), that responds directly to the driving force. The potentials at which fast activation occurs under different conditions have been analyzed to yield the potential-pH dependence and the corresponding entropies and enthalpies. The reduced (active) enzyme shows a pK of 7.6; thus, when a one-electron process is assumed, reductive activation at pH < 7 involves a net uptake of one proton (or release of one hydroxide), whereas, at pH > 8, there is no net exchange of protons with solvent. Activation is favored by a large positive entropy, consistent with the release of a ligand and/or relaxation of the structure around the active site.
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Affiliation(s)
- Anne K Jones
- Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, United Kingdom
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9
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Kennepohl P, Solomon EI. Electronic structure contributions to electron-transfer reactivity in iron-sulfur active sites: 1. Photoelectron spectroscopic determination of electronic relaxation. Inorg Chem 2003; 42:679-88. [PMID: 12562181 DOI: 10.1021/ic020330f] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Electronic relaxation, the change in molecular electronic structure as a response to oxidation, is investigated in [FeX(4)](2)(-)(,1)(-) (X = Cl, SR) model complexes. Photoelectron spectroscopy, in conjunction with density functional methods, is used to define and evaluate the core and valence electronic relaxation upon ionization of [FeX(4)](2)(-). The presence of intense yet formally forbidden charge-transfer satellite peaks in the PES data is a direct reflection of electronic relaxation. The phenomenon is evaluated as a function of charge redistribution at the metal center (Deltaq(rlx)) resulting from changes in the electronic structure. This charge redistribution is calculated from experimental core and valence PES data using a valence bond configuration interaction (VBCI) model. It is found that electronic relaxation is very large for both core (Fe 2p) and valence (Fe 3d) ionization processes and that it is greater in [Fe(SR)(4)](2)(-) than in [FeCl(4)](2)(-). Similar results are obtained from DFT calculations. The results suggest that, although the lowest-energy valence ionization (from the redox-active molecular orbital) is metal-based, electronic relaxation causes a dramatic redistribution of electron density ( approximately 0.7ē) from the ligands to the metal center corresponding to a generalized increase in covalency over all M-L bonds. The more covalent tetrathiolate achieves a larger Deltaq(rlx) because the LMCT states responsible for relaxation are significantly lower in energy than those in the tetrachloride. The large observed electronic relaxation can make significant contributions to the thermodynamics and kinetics of electron transfer in inorganic systems.
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Affiliation(s)
- Pierre Kennepohl
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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Tatsumi H, Kano K, Ikeda T. Kinetic Analysis of Fast Hydrogenase Reaction of Desulfovibrio vulgaris Cells in the Presence of Exogenous Electron Acceptors. J Phys Chem B 2000. [DOI: 10.1021/jp002475i] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hirosuke Tatsumi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kenji Kano
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Tokuji Ikeda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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11
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De Lacey AL, Moiroux J, Bourdillon C. Simple formal kinetics for the reversible uptake of molecular hydrogen by [Ni-Fe] hydrogenase from Desulfovibrio gigas. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6560-70. [PMID: 11054107 DOI: 10.1046/j.1432-1327.2000.01748.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Enzymatic electrocatalysis, triggered and monitored by means of cyclic voltammetry, enabled us to achieve quantitative analysis of the kinetics of the hydrogenase catalyzed process, in the 7.8-10.0 pH range, in the presence of an electrochemically generated redox mediator. The quantitative analysis can be carried out by use of a quite simple SRC model. The simplicity of the SRC model is compatible with the existence of multiple redox microstates, which can be combined in a potential adjustable triangular mechanism consisting of three catalytic cycles, which are formally identical from the kinetic point of view. The steps involved in the kinetic control of the reversible process are H2 uptake or production at the Ni-Fe catalytic site and the intermolecular electron transfer between the mediator and the distal [4Fe-4S] cluster. The related rate constants have been determined. For the two accompanying intramolecular electron transfers which proceed at equilibrium, the equilibrium constants were found to be in very good agreement with previously published data.
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Affiliation(s)
- A L De Lacey
- Laboratoire de Technologie Enzymatique, Unité associée au CNRS no. 6022, Université de Technologie de Compiègne, B.P. 20529, Compiègne, France
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12
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De Lacey AL, Santamaria E, Hatchikian EC, Fernandez VM. Kinetic characterization of Desulfovibrio gigas hydrogenase upon selective chemical modification of amino acid groups as a tool for structure-function relationships. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1481:371-80. [PMID: 11018729 DOI: 10.1016/s0167-4838(00)00180-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effect of amino acid residues modification of Desulfovibrio gigas hydrogenase on different activity assays is reported. The first method consisted in the modification of glutamic and aspartic acid residues of the enzyme with ethylenediamine in order to change the polarity of certain regions of the protein surface. The second method consisted in the modification of histidine residues with a Ru complex in order to change the acid-base properties of the histidine residues. The implication of these modifications in the enzyme kinetics has been studied by measuring in parallel the activities of para/ortho hydrogen conversion, deuterium/hydrogen exchange and dyes reduction with hydrogen. Our experimental data support some hypothesis based on the three-dimensional structure of this enzyme: (a) electrostactic interactions between the hydrogenase and the redox partner play an essential role in the kinetics; (b) the histidine ligand and the surrounding acidic residues of the distal [4Fe4S] cluster form the recognition site of the redox partner of the hydrogenase; and (c) histidine residues are involved in the hydron transfer pathway of the hydrogenase.
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Affiliation(s)
- A L De Lacey
- Instituto de Catálisis, C.S.I.C., Campus Universidad Autónoma-Cantoblanco, Madrid, Spain.
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13
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Brugna M, Nitschke W, Toci R, Bruschi M, Giudici-Orticoni MT. First evidence for the presence of a hydrogenase in the sulfur-reducing bacterium Desulfuromonas acetoxidans. J Bacteriol 1999; 181:5505-8. [PMID: 10464227 PMCID: PMC94062 DOI: 10.1128/jb.181.17.5505-5508.1999] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/1999] [Accepted: 06/22/1999] [Indexed: 11/20/2022] Open
Abstract
Hydrogenases, which are ubiquitous in sulfate-reducing bacteria, were previously thought to be absent from Desulfuromonas acetoxidans. For the first time, a hydrogenase from the strict anaerobic sulfur-respiring bacterium D. acetoxidans, grown on ethanol-malate, was detected and enriched. To assay the role of the hydrogenase in the energetic metabolism of D. acetoxidans, we examined the reactivity of the enzyme with polyheme cytochromes from the same bacterium.
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Affiliation(s)
- M Brugna
- Laboratoire de Bioénergétique et Ingénierie des Protéines, UPR 9036 CNRS, Institut de Biologie Structurale et Microbiologie, 13402 Marseille Cedex 20, France
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14
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Nørager S, Legrand P, Pieulle L, Hatchikian C, Roth M. Crystal structure of the oxidised and reduced acidic cytochrome c3from Desulfovibrio africanus. J Mol Biol 1999; 290:881-902. [PMID: 10398589 DOI: 10.1006/jmbi.1999.2917] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Unique among sulphate-reducing bacteria, Desulfovibrio africanus has two periplasmic tetraheme cytochromes c3, one with an acidic isoelectric point which exhibits an unusually low reactivity towards hydrogenase, and another with a basic isoelectric point which shows the usual cytochrome c3reactivity. The crystal structure of the oxidised acidic cytochrome c3of Desulfovibrio africanus (Dva.a) was solved by the multiple anomalous diffraction (MAD) method and refined to 1.6 A resolution. Its structure clearly belongs to the same family as the other known cytochromes c3, but with weak parentage with those of the Desulfovibrio genus and slightly closer to the cytochromes c3of Desulfomicrobium norvegicum. In Dva.a, one edge of heme I is completely exposed to the solvent and surrounded by a negatively charged protein surface. Heme I thus seems to play an important role in electron exchange, in addition to heme III or heme IV which are the electron exchange ports in the other cytochromes c3. The function of Dva.a and the nature of its redox partners in the cell are thus very likely different. By alignment of the seven known 3D structures including Dva.a, it is shown that the structure which is most conserved in all cytochromes c3is the four-heme cluster itself. There is no conserved continuous protein structure which could explain the remarkable invariance of the four-heme cluster. On the contrary, the proximity of the heme edges is such that they interact directly by hydrophobic and van der Waals contacts. This direct interaction, which always involves a pyrrole CA-CB side-chain and its bound protein cysteine Sgammaatom, is probably the main origin of the four-heme cluster stability. The same kind of interaction is found in the chaining of the hemes in other multihemic redox proteins.The crystal structure of reduced Dva. a was solved at 1.9 A resolution. The comparison of the oxidised and reduced structures reveals changes in the positions of water molecules and polar residues which probably result from changes in the protonation state of amino acids and heme propionates. Water molecules are found closer to the hemes and to the iron atoms in the reduced than in the oxidised state. A global movement of a chain fragment in the vicinity of hemes III and IV is observed which result very likely from the electrostatic reorganization of the polypeptide chain induced by reduction.
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Affiliation(s)
- S Nørager
- Laboratoire de Cristallographie et Cristallogénèse des Protéines Institut de Biologie Structurale J.P.Ebel, CEA-CNRS, rue Jules Horowitz, Grenoble, Cedex 1, 38027, France
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Mechanism of the catalysis by Alcaligenes eutrophus H16 hydrogenase of direct electrochemical reduction of NAD+. J Electroanal Chem (Lausanne) 1999. [DOI: 10.1016/s0022-0728(99)00156-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Tatsumi H, Takagi K, Fujita M, Kano K, Ikeda T. Electrochemical study of reversible hydrogenase reaction of Desulfovibrio vulgaris cells with methyl viologen as an electron carrier. Anal Chem 1999; 71:1753-9. [PMID: 10330906 DOI: 10.1021/ac981003l] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An electrode modified with immobilized whole cells of Desulfovibrio vulgaris (Hildenborough) produces an S-shaped voltammogram with both cathodic- and anodic-catalytic-limiting currents in a methyl viologen-containing buffer saturated with H2. Methyl viologen penetrates into the bacterial cells to serve as an electron carrier in the reversible reaction of hydrogenase in the cells and functions as an electron-transfer mediator between the bacterial cells and the electrode, thus producing the catalytic currents for the evolution and consumption of H2. An equation for the catalytic current that takes into account the reversible hydrogenase reaction explains well the shape of the voltammogram. The potential at null current on the voltammogram agrees with the potential determined by potentiometry with the same electrode, which is equal to the redox potential of the H+/H2 couple in the solution--the standard potential of a hydrogen electrode at the pH of the solution. When D. vulgaris cells are suspended in an argon-saturated buffer containing methyl viologen, the suspension produces a catalytic current at a bare glassy carbon electrode for the evolution of H2. Analysis of the current by a theory for a catalytic current for a unidirectional nonlinear enzyme catalysis allows us to determine the kinetic parameters of the reaction between methyl viologen and hydrogenase in intact D. vulgaris cells. Thus we obtain the apparent Michaelis constant for methyl viologen cation radical, K'MV.+ = 0.16 mM, and the apparent catalytic constant (that is, the turnover number per D. vulgaris cell), zkcat,H+ = 1.2 x 10(7) s-1, for the H2 evolution reaction at pH 5.5 and at 25 degrees C, z being the number of hydrogenases contained in a D. vulgaris cell. The bimolecular reaction rate constant, kcat,H+/K'MV.+, of the reaction between methyl viologen cation radical and oxidized hydrogenase in intact D. vulgaris cells is estimated as 4.2 x 10(7) M-1 s-1. Similarly, the bimolecular reaction rate constant, kcat,H2/K'MV2+, of the reaction between methyl viologen and reduced hydrogenase is estimated to be 1.2 x 10(7) M-1 s-1 at pH 9.5 and 25 degrees C. Both rate constants are large enough for the reactions to be diffusion-limited processes.
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Affiliation(s)
- H Tatsumi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan
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Brugna M, Giudici-Orticoni M, Spinelli S, Brown K, Tegoni M, Bruschi M. Kinetics and interaction studies between cytochrome c3 and Fe-only hydrogenase fromDesulfovibrio vulgaris hildenborough. Proteins 1998. [DOI: 10.1002/(sici)1097-0134(19981201)33:4<590::aid-prot11>3.0.co;2-i] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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18
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Kinetic studies on the electron transfer between bacterial c-type cytochromes and metal oxides. J Electroanal Chem (Lausanne) 1998. [DOI: 10.1016/s0022-0728(98)00141-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Lojou E, Bianco P, Bruschi M. Kinetic studies on the electron transfer between various c-type cytochromes and iron (III) using a voltammetric approach. Electrochim Acta 1998. [DOI: 10.1016/s0013-4686(97)10124-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Verhagen MF, Wolbert RB, Hagen WR. Cytochrome c553 from Desulfovibrio vulgaris (Hildenborough). Electrochemical properties and electron transfer with hydrogenase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 221:821-9. [PMID: 8174562 DOI: 10.1111/j.1432-1033.1994.tb18796.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
An electrochemical study of the periplasmic cytochrome c553 of Desulfovibrio vulgaris (Hildenborough) is presented. The dependence of the midpoint potential on temperature and pH was studied with cyclic voltammetry. The voltammograms obtained were reversible and revealed that this cytochrome showed fast electron transfer on a bare glassy carbon electrode. The midpoint potential at pH 7.0 and 25 degrees C was found to be 62 mV versus the normal hydrogen electrode. It was observed that the temperature dependence was discontinuous with a transition temperature at 32 degrees C. The standard reaction entropy at the growth temperature of the organism (37 degrees C) was calculated to be delta S degree ' = -234 J mol-1 K-1. The pH dependence of the midpoint potential could be described with one pK of the oxidized form with a value of 10.6. The second-order rate constant for electron transfer between cytochrome c553 and the Fe-hydrogenase from D. vulgaris (H) was also determined with cyclic voltammetry. The equivalent rate constant for cytochrome c3 and hydrogenase was measured for comparison. The second-order rate constants are 2 x 10(7) M-1 s-1 for cytochrome c553 and 2 x 10(8) M-1 s-1 for cytochrome c3. The kinetic parameters of the hydrogenase for both cytochromes were determined using the spectrophotometric hydrogen consumption assay. With cytochrome c553 this resulted in a Km of 46 microM and a maximum turnover number of 7.1 x 10(2) s-1 in the H2 consumption assay. The values with cytochrome c3 were 17 microM and 6.4 x 10(2) s-1, respectively. The importance of the different kinetic parameters for contrasting models proposed to describe the function of the Fe-hydrogenase are discussed.
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Affiliation(s)
- M F Verhagen
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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