title: The 1.2 A structure of the human sulfite oxidase cytochrome b(5) domain.
abstract: The molybdenum- and iron-containing enzyme sulfite oxidase catalyzes the physiologically vital oxidation of sulfite to sulfate. Sulfite oxidase contains three domains: an N-terminal cytochrome b(5) domain, a central domain harboring the molybdenum cofactor (Moco) and a C-terminal dimerization domain. Oxidation of the substrate sulfite is coupled to the transfer of two electrons to the molybdenum cofactor. Subsequently, these electrons are passed on, one at a time, to the b(5) heme of sulfite oxidase and from there to the soluble electron carrier cytochrome c. The crystal structure of the oxidized human sulfite oxidase cytochrome b(5) domain has been determined at 1.2 A resolution and has been refined to a crystallographic R factor of 0.107 (R(free) = 0.137). A comparison of this structure with other b(5)-type cytochromes reveals distinct structural features present in the sulfite oxidase b(5) domain which promote optimal electron transport between the Moco of sulfite oxidase and the heme of cytochrome c.
authors.affiliation: Department of Pharmacological Sciences and Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-5115, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rudolph
authors.forename: Jean L
authors.initials: JL
authors.lastname: Johnson
authors.forename: K V
authors.initials: KV
authors.lastname: Rajagopalan
authors.forename: Caroline
authors.initials: C
authors.lastname: Kisker
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D015786:Cytochromes b5 / Q000737:chemistry*; D004579:Electron Transport; D006801:Humans; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry*; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: D015786:Cytochromes b5; D050862:Oxidoreductases Acting on Sulfur Group Donors