Soulimane T, Buse G, Bourenkov G P, Bartunik H D, Huber R, Than M E
Rheinisch-Westfälische Technische Hochschule Aachen, Institut für Biochemie, Pauwelsstrasse 30, D-52057 Aachen, Germany.
EMBO J. 2000 Apr 17;19(8):1766-76. doi: 10.1093/emboj/19.8.1766.
Cytochrome c oxidase is a respiratory enzyme catalysing the energy-conserving reduction of molecular oxygen to water. The crystal structure of the ba(3)-cytochrome c oxidase from Thermus thermophilus has been determined to 2.4 A resolution using multiple anomalous dispersion (MAD) phasing and led to the discovery of a novel subunit IIa. A structure-based sequence alignment of this phylogenetically very distant oxidase with the other structurally known cytochrome oxidases leads to the identification of sequence motifs and residues that seem to be indispensable for the function of the haem copper oxidases, e.g. a new electron transfer pathway leading directly from Cu(A) to Cu(B). Specific features of the ba(3)-oxidase include an extended oxygen input channel, which leads directly to the active site, the presence of only one oxygen atom (O(2-), OH(-) or H(2)O) as bridging ligand at the active site and the mainly hydrophobic character of the interactions that stabilize the electron transfer complex between this oxidase and its substrate cytochrome c. New aspects of the proton pumping mechanism could be identified.
细胞色素c氧化酶是一种呼吸酶，催化将分子氧节能还原为水的反应。嗜热栖热菌的ba(3)-细胞色素c氧化酶的晶体结构已通过多波长反常散射（MAD）相位分析确定到2.4埃分辨率，并由此发现了一种新的亚基IIa。将这种在系统发育上相距甚远的氧化酶与其他已知结构的细胞色素氧化酶进行基于结构的序列比对，可鉴定出对于血红素铜氧化酶功能似乎不可或缺的序列基序和残基，例如一条直接从Cu(A)通向Cu(B)的新电子传递途径。ba(3)-氧化酶的特定特征包括一个直接通向活性位点的延长的氧气输入通道、活性位点仅存在一个氧原子（O(2-)、OH(-)或H(2)O）作为桥连配体，以及稳定该氧化酶与其底物细胞色素c之间电子传递复合物的相互作用主要具有疏水性。质子泵浦机制的新方面得以确定。
