title: The tetraheme cytochrome CymA is required for anaerobic respiration with dimethyl sulfoxide and nitrite in Shewanella oneidensis.
abstract: The tetraheme c-type cytochrome, CymA, from Shewanella oneidensis MR-1 has previously been shown to be required for respiration with Fe(III), nitrate, and fumarate [Myers, C. R., and Myers, J. M. (1997) J. Bacteriol. 179, 1143-1152]. It is located in the cytoplasmic membrane where the bulk of the protein is exposed to the periplasm, enabling it to transfer electrons to a series of redox partners. We have expressed and purified a soluble derivative of CymA (CymA(sol)) that lacks the N-terminal membrane anchor. We show here, by direct measurements of electron transfer between the purified proteins, that CymA(sol) efficiently reduces S. oneidensis fumarate reductase. This indicates that no further proteins are required for electron transfer between the quinone pool and fumarate if we assume direct reduction of CymA by quinols. By expressing CymA(sol) in a mutant lacking CymA, we have shown that this soluble form of the protein can complement the defect in fumarate respiration. We also demonstrate that CymA is essential for growth with DMSO (dimethyl sulfoxide) and for reduction of nitrite, implicating CymA in at least five different electron transfer pathways in Shewanella.
authors.affiliation: Institute of Cell and Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK.
authors.forename: Carsten
authors.initials: C
authors.lastname: Schwalb
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Chapman
authors.forename: Graeme A
authors.initials: GA
authors.lastname: Reid
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D019069:Cell Respiration; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D004579:Electron Transport; D005650:Fumarates / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006873:Hydroquinones / Q000378:metabolism; D008969:Molecular Sequence Data; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D016133:Polymerase Chain Reaction; D020592:Shewanella / Q000201:enzymology* / Q000235:genetics; D013385:Succinate Dehydrogenase / Q000378:metabolism*
chemical_list: D003574:Cytochrome c Group; D017931:DNA Primers; D005650:Fumarates; D006873:Hydroquinones; D009573:Nitrites; C017165:cytochrome c(3); C112400:flavocytochrome c3; D013385:Succinate Dehydrogenase; D004121:Dimethyl Sulfoxide