Nakai M, Kinoshita K, Endo T
Department of Chemistry, Faculty of Science, Nagoya University, Japan.
J Biol Chem. 1995 Dec 22;270(51):30571-5. doi: 10.1074/jbc.270.51.30571.
MAS17 (MAS22) is an essential component of the import receptor complex in the yeast mitochondrial outer membrane. MAS17 consists of three distinct domains: the N-terminal cytosolic domain, the internal membrane-spanning domain, and the C-terminal intermembrane space domain. In the present study, we examined the roles of the C-terminal domain of MAS17, which is rich in acidic amino acids, in protein import into mitochondria both in vivo and in vitro. Cells expressing MAS17 delta 120-152, a mutant MAS17 lacking the C-terminal acidic domain, could grow as fast as those expressing wild-type MAS17, while cells expressing MAS17 delta 97-152, a mutant MAS17 lacking both the intermembrane space and the membrane-spanning domains, stopped growing as soon as wild-type MAS17 was depleted. MAS17 delta 120-152 was correctly integrated into the mitochondrial outer membrane like wild-type MAS17. Mitochondria containing MAS17 delta 120-152 instead of wild-type MAS17 could import both authentic and artificial mitochondrial precursor proteins nearly as efficiently as wild-type mitochondria in vitro. These results suggest that the C-terminal intermembrane space domain of MAS17 is not essential for targeting or functions of MAS17.
MAS17（MAS22）是酵母线粒体外膜中输入受体复合物的一个重要组成部分。MAS17由三个不同的结构域组成：N端胞质结构域、内部跨膜结构域和C端膜间隙结构域。在本研究中，我们研究了富含酸性氨基酸的MAS17的C端结构域在体内和体外蛋白质输入线粒体过程中的作用。表达MAS17δ120 - 152（一种缺失C端酸性结构域的突变型MAS17）的细胞生长速度与表达野生型MAS17的细胞一样快，而表达MAS17δ97 - 152（一种同时缺失膜间隙和跨膜结构域的突变型MAS17）的细胞在野生型MAS17耗尽后立即停止生长。MAS17δ120 - 152像野生型MAS17一样正确地整合到线粒体外膜中。含有MAS17δ120 - 152而非野生型MAS17的线粒体在体外导入真实的和人工合成的线粒体前体蛋白的效率几乎与野生型线粒体一样高。这些结果表明，MAS17的C端膜间隙结构域对于MAS17的靶向作用或功能并非必不可少。
