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Wang X, Clément R, Roger M, Bauzan M, Mazurenko I, Poulpiquet AD, Ilbert M, Lojou E. Bacterial Respiratory Chain Diversity Reveals a Cytochrome c Oxidase Reducing O 2 at Low Overpotentials. J Am Chem Soc 2019; 141:11093-11102. [PMID: 31274287 DOI: 10.1021/jacs.9b03268] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome c oxidases (CcOs) are the terminal enzymes in energy-converting chains of microorganisms, where they reduce oxygen into water. Their affinity for O2 makes them attractive biocatalysts for technological devices in which O2 concentration is limited, but the high overpotentials they display on electrodes severely limit their applicative use. Here, the CcO of the acidophilic bacterium Acidithiobacillus ferrooxidans is studied on various carbon materials by direct protein electrochemistry and mediated one with redox mediators either diffusing or co-immobilized at the electrode surface. The entrapment of the CcO in a network of hydrophobic carbon nanofibers permits a direct electrochemical communication between the enzyme and the electrode. We demonstrate that the CcO displays a μM affinity for O2 and reduces O2 at exceptionally high electrode potentials in the range of +700 to +540 mV vs NHE over a pH range of 4-6. The kinetics of interactions between the enzyme and its physiological partners are fully quantified. Based on these results, an electron transfer pathway allowing O2 reduction in the acidic metabolic chain is proposed.
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Affiliation(s)
- Xie Wang
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
| | - Romain Clément
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
| | - Magali Roger
- School of Natural and Environmental Sciences , Newcastle University , Devonshire Building , NE1 7RX , Newcastle upon Tyne , England
| | - Marielle Bauzan
- Aix-Marseille Univ , CNRS, IMM FR 3479, 31 Chemin Aiguier , 13009 Marseille , France
| | - Ievgen Mazurenko
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
| | - Anne de Poulpiquet
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
| | - Marianne Ilbert
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
| | - Elisabeth Lojou
- Aix-Marseille Univ , CNRS, BIP UMR 7281, 31 Chemin Aiguier , CS 70071, 13402 Marseille Cedex 09 , France
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Wang X, Roger M, Clément R, Lecomte S, Biaso F, Abriata LA, Mansuelle P, Mazurenko I, Giudici-Orticoni MT, Lojou E, Ilbert M. Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin. Chem Sci 2018; 9:4879-4891. [PMID: 29910941 PMCID: PMC5982212 DOI: 10.1039/c8sc01615a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 04/30/2018] [Indexed: 12/15/2022] Open
Abstract
Acidithiobacillus ferrooxidans, a chemolithoautotrophic Gram-negative bacterium, has a remarkable ability to obtain energy from ferrous iron oxidation at pH 2. Several metalloproteins have been described as being involved in this respiratory chain coupling iron oxidation with oxygen reduction. However, their properties and physiological functions remain largely unknown, preventing a clear understanding of the global mechanism. In this work, we focus on two metalloproteins of this respiratory pathway, a diheme cytochrome c4 (Cyt c4) and a green copper protein (AcoP) of unknown function. We first demonstrate the formation of a complex between these two purified proteins, which allows homogeneous intermolecular electron-transfer in solution. We then mimic the physiological interaction between the two partners by replacing one at a time with electrodes displaying different chemical functionalities. From the electrochemical behavior of individual proteins, we show that, while electron transfer on AcoP requires weak electrostatic interaction, electron transfer on Cyt c4 tolerates different charge and hydrophobicity conditions, suggesting a pivotal role of this protein in the metabolic chain. The electrochemical study of the proteins incubated together demonstrates an intermolecular electron transfer involving the protein complex, in which AcoP is reduced through the high potential heme of Cyt c4. Modelling of the electrochemical signals at different scan rates allows us to estimate the rate constant of this intermolecular electron transfer in the range of a few s-1. Possible routes for electron transfer in the acidophilic bacterium are deduced.
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Affiliation(s)
- X Wang
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
| | - M Roger
- School of Life Sciences , University of Dundee , Dundee , DD1 5EH , Scotland , UK
| | - R Clément
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
| | - S Lecomte
- Institute for Chemistry and Biology of Membrane and Nano-objects , Allée Geoffroy St Hilaire , 33600 Pessac , France
| | - F Biaso
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
| | - L A Abriata
- Laboratory for Biomolecular Modeling , École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics , AAB014, Station 19 , 1015 Lausanne , Switzerland
| | - P Mansuelle
- Aix Marseille Univ , CNRS , Institut de Microbiologie de la Méditerranée , FR 3479, Plate-forme Protéomique, Marseille Protéomique (MaP), B.P. 71 , 13402 Marseille Cedex 20 , France
| | - I Mazurenko
- School of Biomedical Sciences , Leeds , LS2 9JT , UK
| | - M T Giudici-Orticoni
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
| | - E Lojou
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
| | - M Ilbert
- Aix Marseille Univ , CNRS , IMM , BIP , UMR 7281 , 31 Chemin Aiguier , 13009 Marseille , France . ;
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