Redox-Coupled Crystal Structural Changes in Bovine Heart Cytochrome c Oxidase

摘要

Crystal structures of bovine heart cytochrome c oxidase in the fully oxidized, fully reduced, azide-bound, and carbon monoxide-bound states were determined at 2.30, 2.35, 2.9, and 2.8 angstrom resolution, respectively. An aspartate residue apart from the O_2 reduction site exchanges its effective accessibility to the matrix aqueous phase for One to the cytosolic phase concomitantly with a significant decrease in the pK of its Carboxyl group, on reduction of the metal sites. The movement indicates the aspartate as the proton pumping site. A tyrosine acidified by a covalently linked imidazole nitrogen is a possible proton donor for the O_2 reduction by the enzyme.