Alben J O, Moh P P, Fiamingo F G, Altschuld R A
Proc Natl Acad Sci U S A. 1981 Jan;78(1):234-7. doi: 10.1073/pnas.78.1.234.
Carbon monoxide bound to iron or copper in substrate-reduced mitochondrial cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) from beef heart has been used to explore the structural interaction of the a3 heme-copper pocket at 15 K and 80 K in the dark and in the presence of visible light. The vibrational absorptions of CO measured by a Fourier transform infrared interferometer occur in the dark at 1963 cm-1, with small absorptions near 1952 cm-1, and are due to a3 heme--CO complexes. These disappear in strong visible light and are replaced by a major absorption at 2062 cm-1 and a minor one at 2043 cm-1 due to Cu--CO. Relaxation in the dark is rapid and quantitative at 210 K, but becomes negligible below 140 K. The multiple absorptions indicate structural heterogeneity of cytochrome oxidase in mitochondria. The Cu--CO absorptions (vCO) are similar to those in hemocyanin--CO complexes from molluscs (vCO - 2062 cm-1) and crustaceans (vCO = 2043 cm-1). The 2062 cm-1 Cu--CO absorption of cytochrome oxidase is split into two bands at 15 K. Analysis of spectral data suggest the presence of a very nonpolar heme--Cu pocket in which the heme-CO complex is highly ordered, but in which the Cu--CO complex is much more flexible, especially above 80 K. A function for these structures in oxygen reduction is proposed.
结合于来自牛心的底物还原型线粒体细胞色素c氧化酶（亚铁细胞色素c：氧氧化还原酶，EC 1.9.3.1）中铁或铜的一氧化碳，已被用于在15 K和80 K温度下、黑暗及可见光存在的条件下，探究a3血红素-铜口袋的结构相互作用。通过傅里叶变换红外干涉仪测量的CO的振动吸收，在黑暗中于1963 cm-1处出现，在1952 cm-1附近有小的吸收峰，这归因于a3血红素-CO复合物。这些吸收峰在强可见光下消失，并被由于Cu-CO导致的在2062 cm-1处的主要吸收峰和在2043 cm-1处的次要吸收峰所取代。在210 K时黑暗中的弛豫迅速且定量，但在140 K以下可忽略不计。多重吸收表明线粒体中细胞色素氧化酶的结构异质性。Cu-CO吸收峰（vCO）与来自软体动物（vCO - 2062 cm-1）和甲壳类动物（vCO = 2043 cm-1）的血蓝蛋白-CO复合物中的吸收峰相似。细胞色素氧化酶的2062 cm-1 Cu-CO吸收峰在15 K时分裂为两个谱带。光谱数据分析表明存在一个非常非极性的血红素-铜口袋，其中血红素-CO复合物高度有序，但Cu-CO复合物更加灵活，尤其是在80 K以上。文中提出了这些结构在氧还原中的作用。
