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A trans‐outer membrane porin‐cytochrome protein complex for extracellular electron transfer by G eobacter sulfurreducens PCA
Author(s) -
Liu Yimo,
Wang Zheming,
Liu Juan,
Levar Caleb,
Edwards Marcus J.,
Babauta Jerome T.,
Kennedy David W.,
Shi Zhi,
Beyenal Haluk,
Bond Daniel R.,
Clarke Thomas A.,
Butt Julea N.,
Richardson David J.,
Rosso Kevin M.,
Zachara John M,
Fredrickson James K.,
Shi Liang
Publication year - 2014
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12204
Subject(s) - geobacter sulfurreducens , porin , bacterial outer membrane , cytochrome , periplasmic space , cytochrome c , biology , biochemistry , orfs , chemistry , bacteria , gene , peptide sequence , genetics , biofilm , mitochondrion , escherichia coli , open reading frame , enzyme
Summary The multi‐heme, outer membrane c ‐type cytochrome ( c ‐ C yt) OmcB of G eobacter sulfurreducens was previously proposed to mediate electron transfer across the outer membrane. However, the underlying mechanism has remained uncharacterized. In G . sulfurreducens , the omcB gene is part of two tandem four‐gene clusters, each is predicted to encode a transcriptional factor ( OrfR / OrfS ), a porin‐like outer membrane protein ( OmbB / OmbC ), a periplasmic c‐ type cytochrome ( OmaB / OmaC ) and an outer membrane c ‐ C yt ( OmcB / OmcC ) respectively. Here, we showed that OmbB / OmbC , OmaB / OmaC and OmcB / OmcC of G . sulfurreducens PCA formed the porin‐cytochrome ( P cc) protein complexes, which were involved in transferring electrons across the outer membrane. The isolated P cc protein complexes reconstituted in proteoliposomes transferred electrons from reduced methyl viologen across the lipid bilayer of liposomes to F e( III )‐citrate and ferrihydrite. The pcc clusters were found in all eight sequenced G eobacter and 11 other bacterial genomes from six different phyla, demonstrating a widespread distribution of P cc protein complexes in phylogenetically diverse bacteria. Deletion of ombB‐omaB‐omcB‐orfS‐ombC‐omaC‐omcC gene clusters had no impact on the growth of G . sulfurreducens PCA with fumarate but diminished the ability of G . sulfurreducens PCA to reduce F e( III )‐citrate and ferrihydrite. Complementation with the ombB‐omaB‐omcB gene cluster restored the ability of G . sulfurreducens PCA to reduce F e( III )‐citrate and ferrihydrite.