title: Rhodobacter sphaeroides haem protein: a novel cytochrome with nitric oxide dioxygenase activity.
abstract: Rhodobacter sphaeroides produces a novel cytochrome, designated as SHP (sphaeroides haem protein), that is unusual in having asparagine as a redox-labile haem ligand. The gene encoding SHP is contained within an operon that also encodes a DHC (dihaem cytochrome c) and a membrane-associated cytochrome b. DHC and SHP have been shown to have high affinity for each other at low ionic strength (Kd=0.2 microM), and DHC is able to reduce SHP very rapidly. The reduced form of the protein, SHP2+ (reduced or ferrous SHP), has high affinity for both oxygen and nitric oxide (NO). It has been shown that the oxyferrous form, SHP2+-O2 (oxygen-bound form of SHP), reacts rapidly with NO to produce nitrate, whereas SHP2+-NO (the NO-bound form of SHP) will react with superoxide with the same product formed. It is therefore possible that SHP functions physiologically as a nitric oxide dioxygenase, protecting the organism against NO poisoning, and we propose a possible mechanism for this process.
authors.affiliation: EaStCHEM, School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.
authors.forename: Bor-Ran
authors.initials: BR
authors.lastname: Li
authors.forename: J L Ross
authors.initials: JL
authors.lastname: Anderson
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Mowat
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Miles
authors.forename: Graeme A
authors.initials: GA
authors.lastname: Reid
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Chapman
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism; D006420:Hemeproteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012242:Rhodobacter sphaeroides / Q000737:chemistry* / Q000201:enzymology; D013481:Superoxides / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D006420:Hemeproteins; D009566:Nitrates; C111967:SHP protein, Rhodobacter sphaeroides; D013481:Superoxides; D009569:Nitric Oxide; D010105:Oxygenases; C114415:nitric oxide dioxygenase; D010100:Oxygen