Hartl F U, Schmidt B, Wachter E, Weiss H, Neupert W
Cell. 1986 Dec 26;47(6):939-51. doi: 10.1016/0092-8674(86)90809-3.
The Fe/S protein of complex III is encoded by a nuclear gene, synthesized in the cytoplasm as a precursor with a 32 residue amino-terminal extension, and transported to the outer surface of the inner mitochondrial membrane. Our data suggest the following transport pathway. First, the precursor is translocated via translocation contact sites into the matrix. There, cleavage to an intermediate containing an eight residue extension occurs. The intermediate is then redirected across the inner membrane, processed to the mature subunit, and assembled into complex III. We suggest that the folding and membrane-translocation pathway in the endosymbiotic ancestor of mitochondria has been conserved during evolution of eukaryotic cells; transfer of the gene for Fe/S protein to the nucleus has led to addition of the presequence, which routes the precursor back to its "ancestral" assembly pathway.
复合体III的铁硫蛋白由一个核基因编码，在细胞质中以前体形式合成，前体带有32个氨基酸残基的氨基末端延伸序列，然后被转运到线粒体内膜的外表面。我们的数据表明了以下转运途径。首先，前体通过转运接触位点转运到基质中。在那里，前体被切割成含有8个残基延伸序列的中间体。然后，中间体被重新引导穿过内膜，加工成成熟亚基，并组装到复合体III中。我们认为，线粒体共生祖先中的折叠和膜转运途径在真核细胞进化过程中得以保留；铁硫蛋白基因转移到细胞核导致了前导序列的添加，该序列将前体重新引导回其“祖先”组装途径。
