title: X-ray structure of azide-bound fully oxidized cytochrome c oxidase from bovine heart at 2.9 A resolution.
abstract: Two azide ions were identified, one between the Fe and Cu atoms in the O(2)-reduction site and the other at the transmembrane surface of the enzyme, in the crystal structure of the azide-bound form of bovine heart cytochrome c oxidase at 2.9 A resolution. Two geometries, a mu-1,3 type geometry between the Fe and Cu atoms and a terminal geometry on the Fe atom, are equally possible for an azide ion in the O(2)--reduction site. The other azide molecule was hydrogen bonded to an amide group of an asparagine and a hydroxyl group of tyrosine in a mu-1,1 type geometry. The antisymmetric infrared bands arising from these azide ions, which show essentially identical intensity [Yoshikawa & Caughey (1992), J. Biol. Chem. 267, 9757-9766], strongly suggest terminal binding of the azide to Fe. The electron density of all three imidazole ligands to Cu(B) was clearly seen in the electron-density map of the azide-bound form of bovine heart enzyme, in contrast to the crystal structure of the azide-bound form of the bacterial enzyme [Iwata et al. (1995), Nature (London), 376, 660-669], which lacks one of the three imidazole ligands to Cu(B).
authors.affiliation: Institute for Protein Research, Osaka University, 3-2 Yamada-oka, Suita 565, Japan.
authors.forename: M J
authors.initials: MJ
authors.lastname: Fei
authors.forename: E
authors.initials: E
authors.lastname: Yamashita
authors.forename: N
authors.initials: N
authors.lastname: Inoue
authors.forename: M
authors.initials: M
authors.lastname: Yao
authors.forename: H
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: T
authors.initials: T
authors.lastname: Tsukihara
authors.forename: K
authors.initials: K
authors.lastname: Shinzawa-Itoh
authors.forename: R
authors.initials: R
authors.lastname: Nakashima
authors.forename: S
authors.initials: S
authors.lastname: Yoshikawa
mesh_terms: D000818:Animals; D001386:Azides; D001665:Binding Sites; D002417:Cattle; D003196:Computer Graphics; D003300:Copper; D018360:Crystallography, X-Ray; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism; D007501:Iron; D008929:Mitochondria, Heart / Q000201:enzymology*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D011487:Protein Conformation
chemical_list: D001386:Azides; D003300:Copper; D007501:Iron; D003576:Electron Transport Complex IV