Evidence for a pro-oxidant intermediate in the assembly of cytochrome oxidase
Evidence for a pro-oxidant intermediate in the assembly of cytochrome oxidase
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DOI：
10.1074/jbc.m702379200
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发表时间：
2007-06-15
影响因子：
4.8
通讯作者：
Winge, Dennis R.
中科院分区：
文献类型：
--
作者：
Khalimonchuk, Oleh;Bird, Amanda;Winge, Dennis R.
在细胞色素c氧化酶(CcO)的组装过程中，缺乏两种蛋白质Sco1和Cox11的细胞对过氧化氢的敏感性是由于促氧化剂血红素A-Cox1停滞的中间产物的瞬时积累引起的。这些细胞对过氧化氢的敏感性被COX1表达或血红素A形成的减少所消除，但由于COX15的过度表达而导致的Cox1表达增强或血红素A产生加剧了这些细胞的过氧化敏感性。Cox1和Cox11分别参与了CcO的铜-A和铜-B位的形成。各自的野生型基因抑制了cox1 Delta和cox11 Delta细胞的过氧化敏感性，但与非同源基因没有交叉互补。Sco1和Cox11的铜结合突变等位基因不具有促进CcO组装的功能，但它们各自的零突变具有抑制过氧化氢敏感性的功能。同样，在酵母CcO组装中不起作用的人Sco1能够抑制酵母Sco1 Delta细胞的过氧化敏感性。因此，细胞的呼吸能力和过氧化氢的敏感性之间存在脱节。Cox1 Delta和Cox11 Delta细胞对过氧化氢的敏感性被一种新的线粒体ATPase Afg1的过表达所消除，该酶促进CcO线粒体编码亚基的降解。对CcO组装突变体过氧化氢敏感性的研究揭示了CcO组装过程的新方面。
The hydrogen peroxide sensitivity of cells lacking two proteins, Sco1 and Cox11, important in the assembly of cytochrome c oxidase (CcO), is shown to arise from the transient accumulation of a pro-oxidant heme A-Cox1 stalled intermediate. The peroxide sensitivity of these cells is abrogated by a reduction in either Cox1 expression or heme A formation but exacerbated by either enhanced Cox1 expression or heme A production arising from overexpression of COX15. Sco1 and Cox11 are implicated in the formation of the Cu-A and Cu-B sites of CcO, respectively. The respective wild-type genes suppress the peroxide sensitivities of sco1 Delta and cox11 Delta cells, but no cross-complementation is seen with noncognate genes. Copper-binding mutant alleles of Sco1 and Cox11 that are nonfunctional in promoting the assembly of CcO are functional in suppressing the peroxide sensitivity of their respective null mutants. Likewise, human Sco1 that is nonfunctional in yeast CcO assembly is able to suppress the peroxide sensitivity of yeast sco1 Delta cells. Thus, a disconnect exists between the respiratory capacity of cells and hydrogen peroxide sensitivity. Hydrogen peroxide sensitivity of sco1 Delta and cox11 Delta cells is abrogated by overexpression of a novel mitochondrial ATPase Afg1 that promotes the degradation of CcO mitochondrially encoded subunits. Studies on the hydrogen peroxide sensitivity in CcO assembly mutants reveal new aspects of the CcO assembly process.