title: The role of multihaem cytochromes in the respiration of nitrite in Escherichia coli and Fe(III) in Shewanella oneidensis.
abstract: The periplasmic nitrite reductase system from Escherichia coli and the extracellular Fe(III) reductase system from Shewanella oneidensis contain multihaem c-type cytochromes as electron carriers and terminal reductases. The position and orientation of the haem cofactors in multihaem cytochromes from different bacteria often show significant conservation despite different arrangements of the polypeptide chain. We propose that the decahaem cytochromes of the iron reductase system MtrA, MtrC and OmcA comprise pentahaem 'modules' similar to the electron donor protein, NrfB, from E. coli. To demonstrate this, we have isolated and characterized the N-terminal pentahaem module of MtrA by preparing a truncated form containing five covalently attached haems. UV-visible spectroscopy indicated that all five haems were low-spin, consistent with the presence of bis-His ligand co-ordination as found in full-length MtrA.
authors.affiliation: Centre for Molecular and Structural Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK. tom.clarke@uea.ac.uk
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Clarke
authors.forename: Tracey
authors.initials: T
authors.lastname: Holley
authors.forename: Robert S
authors.initials: RS
authors.lastname: Hartshorne
authors.forename: Jim K
authors.initials: JK
authors.lastname: Fredrickson
authors.forename: John M
authors.initials: JM
authors.lastname: Zachara
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.forename: David J
authors.initials: DJ
authors.lastname: Richardson
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019069:Cell Respiration / Q000502:physiology*; D003574:Cytochrome c Group / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D003580:Cytochromes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology*; D006418:Heme / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009573:Nitrites / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D020592:Shewanella / Q000502:physiology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D003574:Cytochrome c Group; D003580:Cytochromes; C100938:MtrA protein, Bacteria; D009573:Nitrites; D006418:Heme; C022302:cytochrome C-552; C433527:MtrC protein, Shewanella; D010088:Oxidoreductases; C023314:hydroquinone dehydrogenases