Abstract
Bovine heart cytochrome c oxidase is an integral protein incorporated in the mitochondrial inner membrane, which reduces molecular oxygen to water, coupled with pumping protons from matrix side to entermembrane space. The crystal structures in fully oxidized and fully reduced states were determined at 2.30 and 2.35 Å resolutions, respectively. A tyrosine residue has a covalent bond with a histidine residue, a ligand of CuB. An aspartate residue apart from the O2 reduction site exchanges ets effective accessibility to the matrix aqueous phase for one to intermembrane space by a change of oxidation state. The movement indicates that the aspartate serves as a proton pumpong site.
