Tom20 and Tom22 share the common signal recognition pathway in mitochondrial protein import
Tom20 and Tom22 share the common signal recognition pathway in mitochondrial protein import
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DOI：
10.1074/jbc.m708339200
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发表时间：
2008-02-15
影响因子：
4.8
通讯作者：
Endo, Toshiya
中科院分区：
文献类型：
--
作者：
Yamano, Koji;Yatsukawa, Yoh-Ichi;Endo, Toshiya
线粒体前体蛋白精确靶向线粒体需要线粒体表面的Tom20、Tom22和Tom70的受体功能。Tom20是一种主要的输入受体，优先识别线粒体前导序列，而Tom70是一种特殊受体，识别无前导序列的内膜蛋白。Tom22的胞质结构域似乎与Tom20协同作为一种受体发挥作用，但其底物特异性与Tom20有何不同仍不清楚。为了揭示Tom20和Tom22之间在底物特异性上可能存在的差异（如果有的话），我们通过在Tom20和Tom22的受体结构域与跨膜区段之间引入烟草蚀纹病毒蛋白酶的切割位点，在体外删除了线粒体中Tom20或Tom22的受体结构域。然后分析了缺失Tom20或Tom22受体结构域的线粒体在体外输入靶向不同线粒体亚区室的各种线粒体前体蛋白的能力。对于不同的输入途径，受体结构域的缺失对不同线粒体蛋白输入的影响在Tom20和Tom22之间非常相似。因此，Tom20和Tom22显然参与了输入过程中靶向信号识别的同一途径中的相同步骤或连续步骤。
Precise targeting of mitochondrial precursor proteins to mitochondria requires receptor functions of Tom20, Tom22, and Tom70 on the mitochondrial surface. Tom20 is a major import receptor that recognizes preferentially mitochondrial presequences, and Tom70 is a specialized receptor that recognizes presequence-less inner membrane proteins. The cytosolic domain of Tom22 appears to function as a receptor in cooperation with Tom20, but how its substrate specificity differs from that of Tom20 remains unclear. To reveal possible differences in substrate specificities between Tom20 and Tom22, if any, we deleted the receptor domain of Tom20 or Tom22 in mitochondria in vitro by introducing cleavage sites for a tobacco etch virus protease between the receptor domains and transmembrane segments of Tom20 and Tom22. Then mitochondria without the receptor domain of Tom20 or Tom22 were analyzed for their abilities to import various mitochondrial precursor proteins targeted to different mitochondrial subcompartments in vitro. The effects of deletion of the receptor domains on the import of different mitochondrial proteins for different import pathways were quite similar between Tom20 and Tom22. Therefore Tom20 and Tom22 are apparently involved in the same step or sequential steps along the same pathway of targeting signal recognition in import.