Schlossmann J, Lill R, Neupert W, Court D A
Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie der Universität München, Goethestrasse 33, 80 336 München, Germany.
J Biol Chem. 1996 Jul 26;271(30):17890-5. doi: 10.1074/jbc.271.30.17890.
The protein Tom71 is encoded by the open reading frame YHR117w (yeast chromosome VIII) and shares 53% amino acid sequence identity with Tom70, a protein import receptor of the mitochondrial outer membrane. We investigated the cellular function of Tom71 and addressed the question of whether Tom71 and Tom70 fulfill similar functions. Like Tom70, Tom71 is anchored to the mitochondrial outer membrane via its N terminus, thereby exposing a large C-terminal domain to the cytosol. Tom71 is associated with the protein import complex of this membrane and can be cross-linked to a protein with a molecular mass of 30-35 kDa. Disruption of the TOM71 gene does not reduce cell growth, except on nonfermentable carbon sources at elevated temperatures. Deletion of both the TOM71 and TOM70 genes does not acerbate this growth defect. In vitro import studies demonstrated no functional requirement for Tom71 in the import of several preproteins destined for each of the mitochondrial subcompartments. In particular, the import of Tom70-dependent preproteins is minimally affected by the deletion of Tom71, irrespective of the presence or absence of the Tom70 receptor. Thus, despite their strikingly similar biochemical properties, Tom71 and Tom70 do not perform identical functions.
蛋白质Tom71由开放阅读框YHR117w（酵母染色体VIII）编码，与线粒体外膜的蛋白质导入受体Tom70具有53%的氨基酸序列同一性。我们研究了Tom71的细胞功能，并探讨了Tom71和Tom70是否履行相似功能的问题。与Tom70一样，Tom71通过其N端锚定在线粒体外膜上，从而将一个大的C端结构域暴露于细胞质中。Tom71与该膜的蛋白质导入复合物相关，并且可以与分子量为30 - 35 kDa的一种蛋白质交联。TOM71基因的破坏不会降低细胞生长，除非在高温下的非发酵碳源上。TOM71和TOM70基因的缺失并不会加剧这种生长缺陷。体外导入研究表明，对于几种定位于每个线粒体亚区室的前体蛋白的导入，Tom71并无功能需求。特别是，无论Tom70受体是否存在，Tom71的缺失对依赖Tom70的前体蛋白的导入影响极小。因此，尽管Tom71和Tom70具有惊人相似的生化特性，但它们并不执行相同的功能。
