title: Structures of metal sites of oxidized bovine heart cytochrome c oxidase at 2.8 A.
abstract: The high resolution three-dimensional x-ray structure of the metal sites of bovine heart cytochrome c oxidase is reported. Cytochrome c oxidase is the largest membrane protein yet crystallized and analyzed at atomic resolution. Electron density distribution of the oxidized bovine cytochrome c oxidase at 2.8 A resolution indicates a dinuclear copper center with an unexpected structure similar to a [2Fe-2S]-type iron-sulfur center. Previously predicted zinc and magnesium sites have been located, the former bound by a nuclear encoded subunit on the matrix side of the membrane, and the latter situated between heme a3 and CuA, at the interface of subunits I and II. The O2 binding site contains heme a3 iron and copper atoms (CuB) with an interatomic distance of 4.5 A; there is no detectable bridging ligand between iron and copper atoms in spite of a strong antiferromagnetic coupling between them. A hydrogen bond is present between a hydroxyl group of the hydroxyfarnesylethyl side chain of heme a3 and an OH of a tyrosine. The tyrosine phenol plane is immediately adjacent and perpendicular to an imidazole group bonded to CuB, suggesting a possible role in intramolecular electron transfer or conformational control, the latter of which could induce the redox-coupled proton pumping. A phenyl group located halfway between a pyrrole plane of the heme a3 and an imidazole plane liganded to the other heme (heme a) could also influence electron transfer or conformational control.
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Tsukihara
authors.forename: H
authors.initials: H
authors.lastname: Aoyama
authors.forename: E
authors.initials: E
authors.lastname: Yamashita
authors.forename: T
authors.initials: T
authors.lastname: Tomizaki
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: K
authors.initials: K
authors.lastname: Shinzawa-Itoh
authors.forename: R
authors.initials: R
authors.lastname: Nakashima
authors.forename: R
authors.initials: R
authors.lastname: Yaono
authors.forename: S
authors.initials: S
authors.lastname: Yoshikawa
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003300:Copper / Q000032:analysis*; D003460:Crystallization; D018360:Crystallography, X-Ray; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D005583:Fourier Analysis; D006418:Heme / Q000031:analogs & derivatives* / Q000032:analysis; D006860:Hydrogen Bonding; D008274:Magnesium / Q000032:analysis*; D008929:Mitochondria, Heart / Q000201:enzymology; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017494:Proton Pumps; D015032:Zinc / Q000032:analysis*
chemical_list: D017494:Proton Pumps; C027728:heme a; D006418:Heme; D003300:Copper; D003576:Electron Transport Complex IV; D008274:Magnesium; D015032:Zinc; D010100:Oxygen