Extracellular catalysis of environmental substrates by Shewanella oneidensis MR-1 occurs via active sites on the C-terminal domains of MtrC

Morales Florez, Alejandro, Lockwood, Colin, Nash, Benjamin, Edwards, Marcus J., van Wonderen, Jessica H., Sachdeva, Amit, Butt, Julea N. and Clarke, Tom (2025) Extracellular catalysis of environmental substrates by Shewanella oneidensis MR-1 occurs via active sites on the C-terminal domains of MtrC. Protein Science, 34 (8). ISSN 1469-896X

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Abstract

The Gram-negative Shewanellaceae family is well known for its ability to transfer catabolically derived electrons to extracellular terminal electron acceptors through electron conduits that permeate the outer membrane. The primary conduit is MtrCAB, a trimeric porin-cytochrome complex that contains the cell surface exposed decaheme cytochrome MtrC. This donates electrons to extracellular substrates, including OmcA, soluble metals, organic electron shuttles, and insoluble metal oxides. However, it is not clear whether this broad substrate specificity requires specific sites for binding and reduction, or whether reduction occurs through non-specific interactions near exposed hemes on the cytochrome surface. Shewanella oneidensis MtrC is composed of four domains, with the hemes closely packed and distributed evenly between domains II and IV. The domains are arranged to allow electron transport across the cytochrome via interdomain electron transfer, but the significance of this conserved feature is not understood. Here we use site-directed mutagenesis to generate an MtrC variant that is comprised only of domains I and II (MtrC DI,II). The properties of this MtrC DI,II are effectively identical to domains I and II of full-length MtrC. Whole-cell assays revealed that S. oneidensis cells replacing full-length MtrC with MtrC DI,II had significantly lower rates of OmcA, flavin mononucleotide, and Fe(III) citrate reduction. Our results demonstrate that MtrC domains III and IV contain sites for association of specific substrates, enabling the reduction of extracellular electron acceptors in S. oneidensis.

Item Type: Article
Additional Information: The authors wish to thank the staff at beamline I24 at Diamond Light Source for assistance with data collection and crystal testing (proposal number mx25108), and Liang Shi for Shewanella strains. They are also grateful to David Richardson and Joshua Burton for insightful discussion.
Uncontrolled Keywords: shewanella,c-type cytochrome,electron transfer,flavin,heme chain,microbe–mineral interface,molecular biology,biochemistry ,/dk/atira/pure/subjectarea/asjc/1300/1312
Faculty \ School: Faculty of Science > School of Biological Sciences
Faculty of Science > School of Chemistry, Pharmacy and Pharmacology
Faculty of Science
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Life Processes
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
Faculty of Science > Research Groups > Wolfson Centre for Advanced Environmental Microbiology
Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Groups > Energy Materials Laboratory
Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
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Depositing User: LivePure Connector
Date Deposited: 06 Aug 2025 08:30
Last Modified: 06 Aug 2025 08:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/100058
DOI: 10.1002/pro.70243

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