title: The octahaem SirA catalyses dissimilatory sulfite reduction in Shewanella oneidensis MR-1.
abstract: Shewanella oneidensis MR-1 is a metal reducer that uses a large number of electron acceptors including thiosulfate, polysulfide and sulfite. The enzyme required for thiosulfate and polysulfide respiration has been recently identified, but the mechanisms of sulfite reduction remained unexplored. Analysis of MR-1 cultures grown anaerobically with sulfite suggested that the dissimilatory sulfite reductase catalyses six-electron reduction of sulfite to sulfide. Reduction of sulfite required menaquinones but was independent of the intermediate electron carrier CymA. Furthermore, the terminal sulfite reductase, SirA, was identified as an octahaem c cytochrome with an atypical haem binding site. The sulfite reductase of S. oneidensis MR-1 does not appear to be a sirohaem enzyme, but represents a new class of sulfite reductases. The gene that encodes SirA is located within a 10-gene locus that is predicted to encode a component of a specialized haem lyase, a menaquinone oxidase and copper transport proteins. This locus was identified in the genomes of several Shewanella species and appears to be linked to the ability of these organisms to reduce sulfite under anaerobic conditions.
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, WI 53211, USA.Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Sheetal
authors.initials: S
authors.lastname: Shirodkar
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, WI 53211, USA.Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Reed
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, WI 53211, USA.Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Margie
authors.initials: M
authors.lastname: Romine
authors.affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, WI 53211, USA.Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Daad
authors.initials: D
authors.lastname: Saffarini
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D009154:Mutation; D010084:Oxidation-Reduction; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics / Q000378:metabolism*; D020592:Shewanella / Q000201:enzymology* / Q000235:genetics; D013447:Sulfites / Q000378:metabolism*; D024482:Vitamin K 2 / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D013447:Sulfites; D024482:Vitamin K 2; D050862:Oxidoreductases Acting on Sulfur Group Donors