Wright R M, Dircks L K, Poyton R O
J Biol Chem. 1986 Dec 25;261(36):17183-91.
The gene COX9 for subunit VIIa of cytochrome c oxidase from Saccharomyces cerevisiae has been cloned with the aid of an oligonucleotide probe. From the nucleotide sequence of COX9, we deduce that subunit VIIa is derived from a precursor that is 59 amino acids in length (Mr = 6963). This precursor is longer than mature subunit VIIa by one amino acid at its NH2 terminus and four amino acids at its COOH terminus. COX9 exists as a single copy in the haploid genome of S. cerevisiae and produces one major transcript. When the genomic copy of COX9 is removed, cells lack a functional cytochrome c oxidase holoenzyme. From the predicted secondary structure of subunit VIIa, previous data concerning its relationship to the lipid bilayer of the inner membrane and the location of its hydrophobic domains (Power, S.D., Lochrie, M.A., and Poyton, R.O. (1986) J. Biol. Chem. 261, 9206-9209) and the finding that it is essential for the holoenzyme, we propose a model for subunit VIIa which suggests that this small integral protein plays a role in holoenzyme assembly or stability.
借助寡核苷酸探针克隆了来自酿酒酵母的细胞色素c氧化酶VIIa亚基的COX9基因。根据COX9的核苷酸序列，我们推断VIIa亚基来源于一个长度为59个氨基酸（Mr = 6963）的前体。这个前体在其NH2末端比成熟的VIIa亚基多一个氨基酸，在其COOH末端多四个氨基酸。COX9在酿酒酵母的单倍体基因组中以单拷贝形式存在，并产生一种主要转录本。当COX9的基因组拷贝被去除时，细胞缺乏功能性的细胞色素c氧化酶全酶。根据VIIa亚基的预测二级结构、先前关于其与内膜脂质双层的关系及其疏水结构域位置的数据（Power, S.D., Lochrie, M.A., and Poyton, R.O. (1986) J. Biol. Chem. 261, 9206 - 9209）以及它对全酶至关重要这一发现，我们提出了一个关于VIIa亚基的模型，该模型表明这种小的整合蛋白在全酶组装或稳定性中起作用。
