Reaction mechanism of bovine heart cytochrome c oxidase.
The 1.9 A resolution X-ray structure of the O2 reduction site of bovine heart cytochrome c oxidase in the fully reduced state indicates trigonal planar coordination of CuB by three histidine residues. One of the three histidine residues has a covalent link to a tyrosine residue to ensure retention of the tyrosine at the O2 reduction site. These moieties facilitate a four electron reduction of O2, and prevent formation of active oxygen species. The combination of a redox-coupled conformational change of an aspartate residue (Asp51) located near the intermembrane surface of the enzyme molecule and the existence of a hydrogen bond network connecting Asp51 to the matrix surface suggest that the proton-pumping process is mediated at Asp51. Mutation analyses using a gene expression system of the Asp51-containing enzyme subunit yield results in support of the proposal that Asp51 plays a critical role in the proton pumping process.
Yoshikawa
Shinya
S
Department of Life Science, University of Hyogo, Kamigohri Akoh, Hyogo 678-1297, Japan. yoshi@sci.u-hyogo.ac.jp
Muramoto
Kazumasa
K
Shinzawa-Itoh
Kyoko
K
Aoyama
Hiroshi
H
Tsukihara
Tomitake
T
Ogura
Takashi
T
Shimokata
Kunitoshi
K
Katayama
Yukie
Y
Shimada
Hideo
H
D000818:Animals; D001692:Biological Transport; D002417:Cattle; D018360:Crystallography, X-Ray; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000502:physiology; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D009206:Myocardium / Q000201:enzymology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000502:physiology; D017494:Proton Pumps / Q000502:physiology; D011522:Protons; D013059:Spectrum Analysis, Raman
D017494:Proton Pumps; D011522:Protons; D003576:Electron Transport Complex IV; D010100:Oxygen