Esaki Masatoshi, Kanamori Takashi, Nishikawa Shuh-ichi, Shin Injae, Schultz Peter G, Endo Toshiya
Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
Nat Struct Biol. 2003 Dec;10(12):988-94. doi: 10.1038/nsb1008. Epub 2003 Nov 2.
Mitochondria contain the translocator of the outer mitochondrial membrane (TOM) for protein entry into the organelle, and its subunit Tom40 forms a protein-conducting channel. Here we report the role of Tom40 in protein translocation across the membrane. The site-specific photocrosslinking experiment revealed that translocating unfolded or loosely folded precursor segments of up to 90 residues can be associated with Tom40. Purified Tom40 bound to non-native proteins and suppressed their aggregation when they are prone to aggregate. A denatured protein bound to the Tom40 channel blocked the protein import into mitochondria. These results indicate that, in contrast to the nonstick tunnel of the ribosome for polypeptide exit, the Tom40 channel offers an optimized environment to translocating non-native precursor proteins by preventing their aggregation.
线粒体含有外膜转位酶（TOM），用于蛋白质进入该细胞器，其亚基Tom40形成一个蛋白质传导通道。在此，我们报告Tom40在蛋白质跨膜转运中的作用。位点特异性光交联实验表明，转运长达90个残基的未折叠或松散折叠的前体片段可与Tom40相关联。纯化的Tom40与非天然蛋白质结合，并在它们易于聚集时抑制其聚集。与Tom40通道结合的变性蛋白质会阻断蛋白质导入线粒体。这些结果表明，与核糖体用于多肽输出的不粘通道相反，Tom40通道通过防止非天然前体蛋白质聚集，为其转运提供了一个优化的环境。
