Kozjak Vera, Wiedemann Nils, Milenkovic Dusanka, Lohaus Christiane, Meyer Helmut E, Guiard Bernard, Meisinger Chris, Pfanner Nikolaus
Institut für Biochemie und Molekularbiologie, Universität Freiburg, D-79104 Freiburg, Germany.
J Biol Chem. 2003 Dec 5;278(49):48520-3. doi: 10.1074/jbc.C300442200. Epub 2003 Oct 21.
The preprotein translocase of the outer mitochondrial membrane (TOM complex) contains one essential subunit, the channel Tom40. The assembly pathway of the precursor of Tom40 involves the TOM complex and the sorting and assembly machinery (SAM complex) with the non-essential subunit Mas37. We have identified Sam50, the second essential protein of the mitochondrial outer membrane. Sam50 contains a beta-barrel domain conserved from bacteria to man and is a subunit of the SAM complex. Yeast mutants of Sam50 are defective in the assembly pathways of Tom40 and the abundant outer membrane protein porin, while the import of matrix proteins is not affected. Thus the protein sorting and assembly machinery of the mitochondrial outer membrane involves an essential, conserved protein.
线粒体外膜前体蛋白转运酶（TOM复合体）包含一个必需亚基，即通道蛋白Tom40。Tom40前体的组装途径涉及TOM复合体以及与非必需亚基Mas37相关的分选与组装机制（SAM复合体）。我们已鉴定出线粒体外膜的第二个必需蛋白Sam50。Sam50含有一个从细菌到人类都保守的β桶结构域，是SAM复合体的一个亚基。Sam50的酵母突变体在Tom40和丰富的外膜蛋白孔蛋白的组装途径中存在缺陷，而基质蛋白的导入不受影响。因此，线粒体外膜的蛋白质分选与组装机制涉及一种必需的保守蛋白。
