Issue 21, 2018

Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin

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.

Graphical abstract: Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin

Supplementary files

Article information

Article type
Edge Article
Submitted
09 Apr 2018
Accepted
30 Apr 2018
First published
01 May 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 4879-4891

Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin

X. Wang, M. Roger, R. Clément, S. Lecomte, F. Biaso, L. A. Abriata, P. Mansuelle, I. Mazurenko, M. T. Giudici-Orticoni, E. Lojou and M. Ilbert, Chem. Sci., 2018, 9, 4879 DOI: 10.1039/C8SC01615A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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