title: A sulfite respiration pathway from Thermus thermophilus and the key role of newly identified cytochrome c₅₅₀.
abstract: Sulfite, produced for instance during amino acid metabolism, is a very reactive and toxic compound. Various detoxification mechanisms exist, but sulfite oxidoreductases (SORs) are one of the major actors in sulfite remediation in bacteria and animals. Here we describe the existence of an operon in the extreme thermophilic bacterium Thermus thermophilus HB8 encoding both a SOR and a diheme c-type cytochrome. The in vitro analysis clearly showed that the newly identified cytochrome c₅₅₀ acts as an acceptor of the electrons generated by the SOR enzyme during the oxidation of sulfite. The electrons are then rapidly shuttled via cytochrome c₅₅₂ to the terminal ba₃- and caa₃-type oxidases, thereby unveiling a novel electron transfer pathway, linking sulfite oxidation to oxygen reduction in T. thermophilus: sulfite → SOR(HB8) → cytochrome c₅₅₀ → cytochrome c₅₅₂ → ba₃ oxidase/caa₃ oxidase → O₂. The description of the complete pathway reveals that electrons generated during sulfite oxidation by the SOR are funneled into the respiratory chain, participating in the energy production of T. thermophilus.
authors.affiliation: Chemical and Environmental Science Department, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Robin
authors.forename: Marzia
authors.initials: M
authors.lastname: Arese
authors.forename: Elena
authors.initials: E
authors.lastname: Forte
authors.forename: Paolo
authors.initials: P
authors.lastname: Sarti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Giuffrè
authors.forename: Tewfik
authors.initials: T
authors.lastname: Soulimane
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport; D053858:Metabolic Networks and Pathways; D010084:Oxidation-Reduction; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000235:genetics / Q000378:metabolism; D013447:Sulfites / Q000378:metabolism*; D016963:Thermus thermophilus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D013447:Sulfites; C031732:cytochrome C-550; D050862:Oxidoreductases Acting on Sulfur Group Donors