Teintze M, Slaughter M, Weiss H, Neupert W
J Biol Chem. 1982 Sep 10;257(17):10364-71.
The precursor proteins to the subunits of ubiquinol:cytochrome c reductase (cytochrome bc1 complex) of Neurospora crassa were synthesized in a reticulocyte lysate. These precursors were immunoprecipitated with antibodies prepared against the individual subunits and compared to the mature subunits immunoprecipitated or isolated from mitochondria. Most subunits were synthesized as precursors with larger apparent molecular weights (subunits I, 51,500 versus 50,000; subunit II, 47,500 versus 45,000; subunit IV (cytochrome c1), 38,000 versus 31,000; subunit V (Fe-S protein), 28,000 versus 25,000; subunit VII, 12,000 versus 11,500; subunit VIII, 11,600 versus 11,200). Subunit VI (14,000) was synthesized with the same apparent molecular weight. The post-translational transfer of subunits I, IV, V, and VII was studied in an in vitro system employing reticulocyte lysate and isolated mitochondria. The transfer and proteolytic processing of these precursors was found to be dependent on the mitochondrial membrane potential. In the transfer of cytochrome c1, the proteolytic processing appears to take place in two separate steps via an intermediate both in vivo and in vitro. In vivo, the intermediate form accumulated when cells were kept at 8 degrees C and was chased into mature cytochrome c1 at 25 degrees C. Both processing steps were energy-dependent.
细胞色素c还原酶（细胞色素bc1复合体）亚基的前体蛋白是在网织红细胞裂解物中合成的。这些前体蛋白用针对各个亚基制备的抗体进行免疫沉淀，并与从线粒体中免疫沉淀或分离出的成熟亚基进行比较。大多数亚基合成时为前体，具有较大的表观分子量（亚基I，51,500对50,000；亚基II，47,500对45,000；亚基IV（细胞色素c1），38,000对31,000；亚基V（铁硫蛋白），28,000对25,000；亚基VII，12,000对11,500；亚基VIII，11,600对11,200）。亚基VI（14,000）合成时具有相同的表观分子量。利用网织红细胞裂解物和分离的线粒体的体外系统研究了亚基I、IV、V和VII的翻译后转运。发现这些前体的转运和蛋白水解加工依赖于线粒体膜电位。在细胞色素c1的转运过程中，蛋白水解加工似乎在体内和体外都通过一个中间体分两个独立步骤进行。在体内，当细胞保持在8℃时，中间形式积累，在25℃时被追踪到成熟的细胞色素c1。两个加工步骤都依赖能量。
