Nobrega M P, Nobrega F G, Tzagoloff A
Departmento de Biologia, Universidade de Sao Paulo, Brazil.
J Biol Chem. 1990 Aug 25;265(24):14220-6.
Respiratory-defective mutants of Saccharomyces cerevisiae assigned to pet complementation group G19 lack cytochrome oxidase activity and cytochromes a and a3. The enzyme deficiency is caused by recessive mutations in the nuclear gene COX10. Analyses of cytochrome oxidase subunits suggest that the product of COX10 provides an essential function at a posttranslational stage of enzyme assembly. The wild type COX10 gene has been cloned by transformation of a mutant from complementation group G19 with a yeast genomic library. Based on the nucleotide sequence of COX10, the primary translation product has an Mr of 52,000. The amino-terminal 190 residues constitute a hydrophilic domain while the carboxyl-terminal region is hydrophobic and has nine potential membrane-spanning segments. The sequence of the carboxyl-terminal hydrophobic region is homologous to an unidentified protein encoded by a reading frame (ORF1) located in one of the cytochrome oxidase operons of Paracoccus denitrificans. The two proteins share 24% identical residues and exhibit very similar hydrophobicity profiles. The bacterial homolog, however, lacks the hydrophilic amino-terminal region of the yeast protein.
被归为pet互补群G19的酿酒酵母呼吸缺陷型突变体缺乏细胞色素氧化酶活性以及细胞色素a和a3。这种酶缺陷是由核基因COX10中的隐性突变引起的。对细胞色素氧化酶亚基的分析表明，COX10的产物在酶组装的翻译后阶段提供了一种必需功能。通过用酵母基因组文库转化互补群G19的一个突变体，野生型COX10基因已被克隆。根据COX10的核苷酸序列，初级翻译产物的分子量为52,000。氨基末端的190个残基构成一个亲水区，而羧基末端区域是疏水的，有九个潜在的跨膜片段。羧基末端疏水区域的序列与由位于反硝化副球菌细胞色素氧化酶操纵子之一中的一个阅读框（ORF1）编码的一种未鉴定蛋白质同源。这两种蛋白质有24%的相同残基，并表现出非常相似的疏水性图谱。然而，细菌同源物缺乏酵母蛋白质的亲水性氨基末端区域。
