Behrens M, Michaelis G, Pratje E
Botanisches Institut, Universität Düsseldorf, Federal Republic of Germany.
Mol Gen Genet. 1991 Aug;228(1-2):167-76. doi: 10.1007/BF00282462.
The nuclear yeast mutant pet ts2858 is defective in the removal of pre-sequences from the mitochondrially encoded cytochrome oxidase subunit II (COXII) and the processing intermediate of cytochrome b2 (Cytb2), a nuclear gene product. In order to identify the genetic lesion in this mutant we have cloned and characterized a DNA region which complements the pet ts2858 mutation. The DNA sequence revealed three open reading frames, one of which is responsible for the complementation. A 570 bp reading frame represents the structural gene PET2858, as demonstrated by in vitro mutagenesis, gene expression from a foreign promoter, and allelism tests. PET2858 encodes a 21.4 kDa protein, which is essential for growth on non-fermentable carbon sources and for the proteolytic processing of COXII and the Cytb2 intermediate. When the N-terminus of the PET2858 protein is fused to a reporter protein, the resulting hybrid molecule is imported into mitochondria. Interestingly, the N-terminal half of the deduced PET2858 protein exhibits 30.7% amino acid identity to the leader peptidase of Escherichia coli. These results suggest that PET2858 codes for a mitochondrial inner membrane protease (IMP1) or at least a subunit of it. This protease is involved in protein processing and export from the mitochondrial matrix.
核酵母突变体pet ts2858在从线粒体编码的细胞色素氧化酶亚基II（COXII）和细胞色素b2（Cytb2，一种核基因产物）的加工中间体中去除前序列方面存在缺陷。为了鉴定该突变体中的遗传损伤，我们克隆并表征了一个与pet ts2858突变互补的DNA区域。DNA序列揭示了三个开放阅读框，其中一个负责互补作用。一个570 bp的阅读框代表结构基因PET2858，体外诱变、来自外源启动子的基因表达以及等位性测试证明了这一点。PET2858编码一种21.4 kDa的蛋白质，该蛋白质对于在非发酵碳源上生长以及COXII和Cytb2中间体的蛋白水解加工至关重要。当PET2858蛋白的N末端与报告蛋白融合时，产生的杂合分子会被导入线粒体。有趣的是，推导的PET2858蛋白的N末端一半与大肠杆菌的前导肽酶具有30.7%的氨基酸同一性。这些结果表明PET285编码一种线粒体内膜蛋白酶（IMP1）或至少是其一个亚基。这种蛋白酶参与蛋白质加工和从线粒体基质输出。
