Powers L, Lauraeus M, Reddy K S, Chance B, Wikström M
National Center for the Design of Molecular Function, Utah State University, Logan 84322.
Biochim Biophys Acta. 1994 Jan 4;1183(3):504-12. doi: 10.1016/0005-2728(94)90078-7.
Cytochrome aa3-600 is a terminal quinol oxidase of Bacillus subtilis, belonging to the large family of structurally and functionally related respiratory enzymes to which the mitochondrial cytochrome c oxidase also belongs. However, the CuA center typical of the cytochrome c oxidases is lacking from cytochrome aa3-600. The presence of only one copper, viz. CuB of the binuclear heme iron-copper site, makes cytochrome aa3-600 especially suitable for XAS analysis of this structure. Cu and Fe XAS data for fully oxidized cytochrome aa3-600 indicate a structure for the binuclear site similar to that previously reported for mitochondrial cytochrome c oxidase (see Powers et al. (1981) Biophys. J. 34, 465-468). Heme Fea3 has a proximal histidine nitrogen ligand 2.10 +/- 0.02 A from the iron, and a distal S or Cl ligand at 2.36 +/- 0.03 A. The latter is also a ligand of CuB (2.21 +/- 0.02 A), and apparently forms a bridge between the two metals which are 3.70 +/- 0.06 A apart. CuB has two more close-lying ligands at 1.95 +/- 0.02 A, which are likely histidine nitrogens. The similarity between EXAFS of CuB and type 1 'blue' copper is contrasted to EPR and optical spectroscopic properties of CuB, and the nature of the bridging ligand is discussed.
细胞色素aa3-600是枯草芽孢杆菌的一种末端醌氧化酶，属于结构和功能相关的呼吸酶大家族，线粒体细胞色素c氧化酶也属于该家族。然而，细胞色素aa3-600缺乏细胞色素c氧化酶典型的CuA中心。仅存在一种铜，即双核血红素铁-铜位点的CuB，使得细胞色素aa3-600特别适合对该结构进行X射线吸收光谱（XAS）分析。完全氧化的细胞色素aa3-600的铜和铁XAS数据表明，双核位点的结构与先前报道的线粒体细胞色素c氧化酶的结构相似（见Powers等人（1981年），《生物物理学杂志》34卷，465 - 468页）。血红素Fea3有一个距铁2.10 +/- 0.02 Å的近端组氨酸氮配体，以及一个在2.36 +/- 0.03 Å的远端硫或氯配体。后者也是CuB的配体（2.21 +/- 0.02 Å），并且显然在相距3.70 +/- 0.06 Å的两种金属之间形成了一个桥。CuB在1.95 +/- 0.02 Å处还有另外两个紧密相邻的配体，它们可能是组氨酸氮。将CuB的扩展X射线吸收精细结构（EXAFS）与1型“蓝色”铜的EXAFS之间的相似性与CuB的电子顺磁共振（EPR）和光学光谱性质进行了对比，并讨论了桥连配体的性质。
