title: Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals.
abstract: The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decaheme cytochromes, MtrC and MtrA, brought together inside a transmembrane porin, MtrB, to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system containing a pool of internalized electron carriers was used to investigate how the topology of the MtrCAB complex relates to its ability to transport electrons across a lipid bilayer to externally located Fe(III) oxides. With MtrA facing the interior and MtrC exposed on the outer surface of the phospholipid bilayer, the established in vivo orientation, electron transfer from the interior electron carrier pool through MtrCAB to solid-phase Fe(III) oxides was demonstrated. The rates were 10(3) times higher than those reported for reduction of goethite, hematite, and lepidocrocite by S. oneidensis, and the order of the reaction rates was consistent with those observed in S. oneidensis cultures. In contrast, established rates for single turnover reactions between purified MtrC and Fe(III) oxides were 10(3) times lower. By providing a continuous flow of electrons, the proteoliposome experiments demonstrate that conduction through MtrCAB directly to Fe(III) oxides is sufficient to support in vivo, anaerobic, solid-phase iron respiration.
authors.affiliation: Centre for Molecular and Structural Biochemistry, School of Biological Sciences, and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: Gaye F
authors.initials: GF
authors.lastname: White
authors.forename: Zhi
authors.initials: Z
authors.lastname: Shi
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.forename: Zheming
authors.initials: Z
authors.lastname: Wang
authors.forename: Alice C
authors.initials: AC
authors.lastname: Dohnalkova
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Marshall
authors.forename: James K
authors.initials: JK
authors.lastname: Fredrickson
authors.forename: John M
authors.initials: JM
authors.lastname: Zachara
authors.forename: Julea N
authors.initials: JN
authors.lastname: Butt
authors.forename: David J
authors.initials: DJ
authors.lastname: Richardson
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clarke
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism; D003580:Cytochromes / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology*; D005290:Ferric Compounds / Q000378:metabolism*; D015151:Immunoblotting; D008958:Models, Molecular; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism*; D020592:Shewanella / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003574:Cytochrome c Group; D003580:Cytochromes; D005290:Ferric Compounds; C100938:MtrA protein, Bacteria; C116147:MtrB protein, Shewanella putrefaciens; D046912:Multiprotein Complexes; C433527:MtrC protein, Shewanella
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