Characterization of the inner membrane cytochrome ImcH from Geobacter reveals its importance for extracellular electron transfer and energy conservation

Pimenta, Andreia I., Paquete, Catarina M., Morgado, Leonor, Edwards, Marcus J., Clarke, Thomas A. ORCID: https://orcid.org/0000-0002-6234-1914, Salgueiro, Carlos A., Pereira, Inês A. C. and Duarte, Américo G. (2023) Characterization of the inner membrane cytochrome ImcH from Geobacter reveals its importance for extracellular electron transfer and energy conservation. Protein Science, 32 (11). ISSN 1469-896X

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Abstract

Electroactive bacteria combine the oxidation of carbon substrates with an extracellular electron transfer (EET) process that discharges electrons to an electron acceptor outside the cell. This process involves electron transfer through consecutive redox proteins that efficiently connect the inner membrane to the cell exterior. In this study, we isolated and characterized the quinone-interacting membrane cytochrome c ImcH from Geobacter sulfurreducens, which is involved in the EET process to high redox potential acceptors. Spectroscopic and electrochemical studies show that ImcH hemes have low midpoint redox potentials, ranging from −150 to −358 mV, and connect the oxidation of the quinol-pool to EET, transferring electrons to the highly abundant periplasmic cytochrome PpcA with higher affinity than to its homologues. Despite the larger number of hemes and transmembrane helices, the ImcH structural model has similarities with the NapC/NirT/NrfH superfamily, namely the presence of a quinone-binding site on the P-side of the membrane. In addition, the first heme, likely involved on the quinol oxidation, has apparently an unusual His/Gln coordination. Our work suggests that ImcH is electroneutral and transfers electrons and protons to the same side of the membrane, contributing to the maintenance of a proton motive force and playing a central role in recycling the menaquinone pool.

Item Type:	Article
Uncontrolled Keywords:	sdg 7 - affordable and clean energy ,/dk/atira/pure/sustainabledevelopmentgoals/affordable_and_clean_energy
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	LivePure Connector
Date Deposited:	24 Nov 2023 02:19
Last Modified:	02 Oct 2024 01:38
URI:	https://ueaeprints.uea.ac.uk/id/eprint/93738
DOI:	10.1002/pro.4796

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