Juin P, Thieffry M, Henry J P, Vallette F M
Service de Neurobiologie Physico-Chimique, Centre National de la Recherche Scientifique, Unité Propre de Recherche 9071, Institut de Biologie Physico-Chimique, 13 rue P. et M. Curie, 75005 Paris, France.
J Biol Chem. 1997 Feb 28;272(9):6044-50. doi: 10.1074/jbc.272.9.6044.
The peptide-sensitive channel (PSC), a cationic channel of the mitochondrial outer membrane, is blocked by synthetic mitochondrial presequences and by nonmitochondrial basic peptides such as dynorphin B(1-13). Both types of peptides are imported into mitochondria. However, the import of dynorphin B(1-13) had to be further characterized since its properties differed from those of the general import pathway used by mitochondrial peptides. Cross-linking experiments with iodinated dynorphin B(1-13) led to the labeling of TOM 40/ISP 42, a component of the protein import machinery of the outer membrane. Accordingly, dynorphin B(1-13) could also be used as a presequence to direct the import of a cytosolic protein into the mitochondria. Pretreatment of intact mitochondria by trypsin removed components capable of discriminating between true mitochondrial presequences and other basic peptides active on the PSC. After proteolysis, both types of peptides appeared to cross the outer membrane through the same pathway. Involvement of the PSC in the translocation complex was shown by immunoprecipitation of the PSC activity by anti-ISP 42 antibodies. Taken together, the present data reinforce the hypothesis that the PSC is the pore responsible for the translocation of protein through the outer membrane.
肽敏感通道（PSC）是线粒体外膜的一种阳离子通道，可被合成的线粒体前序列以及强啡肽B（1-13）等非线粒体碱性肽阻断。这两类肽都可被导入线粒体。然而，由于强啡肽B（1-13）的特性与线粒体肽所使用的一般导入途径不同，其导入过程还需进一步研究。用碘化强啡肽B（1-13）进行的交联实验导致线粒体外膜蛋白导入机制的一个组分TOM 40/ISP 42被标记。因此，强啡肽B（1-13）也可作为前序列来指导胞质蛋白导入线粒体。用胰蛋白酶对完整线粒体进行预处理会去除能够区分真正的线粒体前序列和对PSC有活性的其他碱性肽的组分。蛋白水解后，这两类肽似乎通过相同途径穿过外膜。抗ISP 42抗体对PSC活性进行免疫沉淀，表明PSC参与了转运复合物。综上所述，目前的数据强化了这样一种假说，即PSC是负责蛋白质穿过外膜转运的孔道。
