Côté C, Boulet D
Biochem Biophys Res Commun. 1985 May 31;129(1):240-7. doi: 10.1016/0006-291x(85)91428-7.
The cytoplasmically made subunits 2 (beta) and 3 (gamma) of the H+-ATPase from mammalian mitochondria are synthesized in vitro as larger polypeptides. In contrast, pre-cytochrome c could not, on the basis of its molecular weight, be distinguished from the mature polypeptide. This was shown by programming a reticulocyte lysate with rat heart RNA and immunoprecipitating the labeled translation products with polypeptide-specific antibodies. When a translated lysate containing the precursor to the beta-subunit was incubated with isolated rat spleen mitochondria, it was converted to the mature subunit and was no longer susceptible to externally added trypsin. The conversion to the mature form occurred in the absence of protein synthesis. This post-translational maturation process of the beta-subunit was more efficient when carried out with spleen or liver mitochondria than with heart or kidney mitochondria. The converse relative efficiency was observed when the processing of the precursor to ornithine carbamyltransferase by these mitochondria was examined. These results indicate that mitochondria do not discriminate against tissue-specific mitochondrial proteins. In addition, the observed varying degrees of efficiency of mitochondria from different tissues in importing and processing these two precursors suggest that the activity of precursor(s)-specific translocation-maturation systems varies between different types of mitochondria.
哺乳动物线粒体H⁺ -ATP酶的细胞质亚基2（β）和亚基3（γ）在体外作为较大的多肽合成。相比之下，根据其分子量，细胞色素c前体无法与成熟多肽区分开来。这是通过用大鼠心脏RNA对网织红细胞裂解物进行编程并用多肽特异性抗体免疫沉淀标记的翻译产物来证明的。当将含有β亚基前体的翻译裂解物与分离的大鼠脾脏线粒体一起孵育时，它会转化为成熟亚基，并且不再易受外部添加的胰蛋白酶的作用。向成熟形式的转化在没有蛋白质合成的情况下发生。β亚基的这种翻译后成熟过程在用脾脏或肝脏线粒体进行时比用心脏或肾脏线粒体进行时更有效。当检查这些线粒体对鸟氨酸氨甲酰基转移酶前体的加工时，观察到了相反的相对效率。这些结果表明线粒体不会区分组织特异性线粒体蛋白。此外，观察到来自不同组织的线粒体在导入和加工这两种前体时效率不同，这表明前体特异性转运 - 成熟系统的活性在不同类型的线粒体之间有所不同。
