Yoshikawa S, Shinzawa-Itoh K, Nakashima R, Yaono R, Yamashita E, Inoue N, Yao M, Fei M J, Libeu C P, Mizushima T, Yamaguchi H, Tomizaki T, Tsukihara T
Department of Life Science, Himeji Institute of Technology and CREST, Japan Science and Technology Corporation (JST), Kamigohri Akoh, Hyogo 678-1297, Japan.
Science. 1998 Jun 12;280(5370):1723-9. doi: 10.1126/science.280.5370.1723.
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 O2 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 O2 reduction by the enzyme.
分别在2.30、2.35、2.9和2.8埃分辨率下测定了牛心细胞色素c氧化酶在完全氧化、完全还原、叠氮化物结合和一氧化碳结合状态下的晶体结构。除了O₂还原位点外，一个天冬氨酸残基在金属位点还原时，其与基质水相的有效可及性转变为与胞质相的可及性，同时其羧基的pK值显著降低。该移动表明天冬氨酸是质子泵位点。一个被共价连接的咪唑氮酸化的酪氨酸可能是该酶还原O₂的质子供体。
