title: The structure of the soluble domain of an archaeal Rieske iron-sulfur protein at 1.1 A resolution.
abstract: The first crystal structure of an archaeal Rieske iron-sulfur protein, the soluble domain of Rieske iron-sulfur protein II (soxF) from the hyperthermo-acidophile Sulfolobus acidocaldarius, has been solved by multiple wavelength anomalous dispersion (MAD) and has been refined to 1.1 A resolution. SoxF is a subunit of the terminal oxidase supercomplex SoxM in the plasma membrane of S. acidocaldarius that combines features of a cytochrome bc(1) complex and a cytochrome c oxidase. The [2Fe-2S] cluster of soxF is most likely the primary electron acceptor during the oxidation of caldariella quinone by the cytochrome a(587)/Rieske subcomplex. The geometry of the [2Fe-2S] cluster and the structure of the cluster-binding site are almost identical in soxF and the Rieske proteins from eucaryal cytochrome bc(1) and b(6)f complexes, suggesting a strict conservation of the catalytic mechanism. The main domain of soxF and part of the cluster-binding domain, though structurally related, show a significantly divergent structure with respect to topology, non-covalent interactions and surface charges. The divergent structure of soxF reflects a different topology of the soxM complex compared to eucaryal bc complexes and the adaptation of the protein to the extreme ambient conditions on the outer membrane surface of a hyperthermo-acidophilic organism.
authors.affiliation: Department of Biosciences at NOVUM, Center for Structural Biochemistry, Karolinska Institutet, Hälsovägen 7-9, S-14157 Huddinge, Sweden.
authors.forename: Heiko
authors.initials: H
authors.lastname: Bönisch
authors.forename: Christian L
authors.initials: CL
authors.lastname: Schmidt
authors.forename: Günter
authors.initials: G
authors.lastname: Schäfer
authors.forename: Rudolf
authors.initials: R
authors.lastname: Ladenstein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002417:Cattle; D018360:Crystallography, X-Ray; D014450:Electron Transport Complex III; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D018583:Pliability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D012995:Solubility; D018724:Spinacia oleracea; D055672:Static Electricity; D016945:Sulfolobus acidocaldarius / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D019843:Archaeal Proteins; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; C037989:Rieske iron-sulfur protein; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III