Nakai M, Harabayashi M, Hase T, Matsubara H
Department of Biology, Faculty of Science, Osaka University.
J Biochem. 1989 Jul;106(1):181-7. doi: 10.1093/oxfordjournals.jbchem.a122811.
The amino-terminal region of a 70 kDa mitochondrial outer membrane protein of yeast and the presequence of cytochrome c1, an inner membrane protein exposed to the intermembrane space, are thought to be responsible for localizing the proteins in their final destinations after synthesis in the cytosol. Gene fusion experiments were used to identify signals that are responsible for protein sorting between the outer and inner mitochondrial membranes. The submitochondrial localization of cytochrome c1 whose presequence was replaced by the amino-terminal region of the 70 kDa mitochondrial outer membrane protein has been investigated. We have also used an in vivo complementation assay to determine whether or not a 70k-cyt c1 fusion protein is functional. Both the first half and all of the presequence of cytochrome c1 can be replaced by the amino-terminal 12 or 29 residues of the 70 kDa protein for transport to the inner membrane and functional assembly into succinate-cytochrome c reductase. However, replacements by the amino-terminal 61 residues of the 70 kDa protein result in exclusive localization of the fusion proteins to the outer membrane, and the fusions cannot be assembled into the enzyme complex. These data indicate that a mitochondrial targeting signal alone is sufficient to direct cytochrome c1 of mature size to the inner membrane.
酵母70 kDa线粒体外膜蛋白的氨基末端区域以及细胞色素c1（一种暴露于膜间隙的内膜蛋白）的前导序列，被认为在胞质溶胶中合成后负责将这些蛋白定位到它们的最终目的地。基因融合实验被用于鉴定负责线粒体外膜和内膜之间蛋白质分选的信号。已经研究了其前导序列被70 kDa线粒体外膜蛋白的氨基末端区域取代的细胞色素c1的亚线粒体定位。我们还使用了体内互补试验来确定70k-cyt c1融合蛋白是否具有功能。细胞色素c1的前导序列的前半部分和全部都可以被70 kDa蛋白的氨基末端12个或29个残基取代，以便转运到内膜并功能性组装成琥珀酸 - 细胞色素c还原酶。然而，被70 kDa蛋白的氨基末端61个残基取代会导致融合蛋白仅定位于外膜，并且这些融合蛋白不能组装成酶复合物。这些数据表明，仅线粒体靶向信号就足以将成熟大小的细胞色素c1引导至内膜。
