Abteilung Membranbiogenese and 2 Abteilung Membranbiogenese Zellbiologie, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany.
J Cell Biol. 2011 Jun 13;193(6):1101-14. doi: 10.1083/jcb.201103132.
Mitochondria contain their own genetic system to express a small number of hydrophobic polypeptides, including cytochrome b, an essential subunit of the bc(1) complex of the respiratory chain. In this paper, we show in yeast that Cbp3, a bc(1) complex assembly factor, and Cbp6, a regulator of cytochrome b translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial ribosomes and that exhibits two important functions in the biogenesis of cytochrome b. On the one hand, the interaction of Cbp3 and Cbp6 with mitochondrial ribosomes is necessary for efficient translation of cytochrome b transcript [corrected]. On the other hand, the Cbp3-Cbp6 complex interacts directly with newly synthesized cytochrome b in an assembly intermediate that is not ribosome bound and that contains the assembly factor Cbp4. Our results suggest that synthesis of cytochrome b occurs preferentially on those ribosomes that have the Cbp3-Cbp6 complex bound to their tunnel exit, an arrangement that may ensure tight coordination of cytochrome b synthesis and assembly.
线粒体含有自己的遗传系统来表达少数疏水性多肽，包括细胞色素 b，这是呼吸链 bc(1) 复合物的必需亚基。本文在酵母中表明，bc(1) 复合物组装因子 Cbp3 和细胞色素 b 翻译的调节剂 Cbp6 形成一个与线粒体核糖体多肽隧道出口相关的复合物，并在细胞色素 b 的生物发生中具有两个重要功能。一方面，Cbp3 和 Cbp6 与线粒体核糖体的相互作用对于细胞色素 b 转录物的有效翻译是必需的。另一方面，Cbp3-Cbp6 复合物与新合成的细胞色素 b 直接相互作用，形成不结合核糖体的组装中间体，其中包含组装因子 Cbp4。我们的结果表明，细胞色素 b 的合成优先发生在那些结合了 Cbp3-Cbp6 复合物到其隧道出口的核糖体上，这种排列可能确保了细胞色素 b 合成和组装的紧密协调。
