Glerum D M, Shtanko A, Tzagoloff A
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
J Biol Chem. 1996 Jun 14;271(24):14504-9. doi: 10.1074/jbc.271.24.14504.
Mutations in the COX17 gene of Saccharomyces cerevisiae cause a respiratory deficiency due to a block in the production of a functional cytochrome oxidase complex. Because cox17 mutants are able to express both the mitochondrially and nuclearly encoded subunits of cytochrome oxidase, the Cox17p most likely affects some late posttranslational step of the assembly pathway. A fragment of yeast nuclear DNA capable of complementing the mutation has been cloned by transformation of the cox17 mutant with a library of genomic DNA. Subcloning and sequencing of the COX17 gene revealed that it codes for a cysteine-rich protein with a molecular weight of 8,057. Unlike other previously described accessory factors involved in cytochrome oxidase assembly, all of which are components of mitochondria, Cox17p is a cytoplasmic protein. The cytoplasmic location of Cox17p suggested that it might have a function in delivery of a prosthetic group to the holoenzyme. A requirement of Cox17p in providing the copper prosthetic group of cytochrome oxidase is supported by the finding that a cox17 null mutant is rescued by the addition of copper to the growth medium. Evidence is presented indicating that Cox17p is not involved in general copper metabolism in yeast but rather has a more specific function in the delivery of copper to mitochondria.
酿酒酵母COX17基因的突变会导致呼吸缺陷，这是由于功能性细胞色素氧化酶复合物的产生受阻所致。由于cox17突变体能够表达细胞色素氧化酶的线粒体编码亚基和核编码亚基，所以Cox17p很可能影响组装途径中某些后期翻译后步骤。通过用基因组DNA文库转化cox17突变体，已克隆出能够互补该突变的酵母核DNA片段。对COX17基因进行亚克隆和测序后发现，它编码一种分子量为8057的富含半胱氨酸的蛋白质。与其他先前描述的参与细胞色素氧化酶组装的辅助因子不同，这些辅助因子都是线粒体的组成成分，而Cox17p是一种细胞质蛋白。Cox17p的细胞质定位表明它可能在向全酶传递辅基方面具有功能。向生长培养基中添加铜可挽救cox17缺失突变体，这一发现支持了Cox17p在提供细胞色素氧化酶的铜辅基方面的必要性。有证据表明，Cox17p不参与酵母中的一般铜代谢，而是在将铜传递到线粒体方面具有更特定的功能。
