The mitochondrial bc1 complex plays an important role in mitochondrial respiration. It transfers electrons from ubiquinol to the soluble electron shuttle cytochrome c and thereby contributes to the proton motive force across the inner mitochondrial membrane. In the yeast Saccharomyces cerevisiae, each monomer consists of three catalytic and seven accessory subunits. The bc1 complex is an obligate homo-dimer in all systems. It is currently not known when exactly during the assembly dimerization occurs. In this study, we determined that the dimer formation is an early event. Specifically, dimerization is mediated by the interaction of a stable tetramer formed by the two Cor subunits, Cor1 and Cor2, that joins assembly intermediate II, containing the fully hemylated cytochrome b and the two small accessory proteins, Qcr7 and Qcr8. Addition of cytochrome c1 and Qcr6 can either occur concomitantly or independently of dimerization. These results reveal a strict order in assembly, where dimerization occurs after stabilization of co-factor acquisition by cytochrome b. Finally, assembly is completed by addition of the remaining subunits.

中文翻译：

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线粒体呼吸链组装过程中bc1复合物二聚化的时间。

线粒体bc1复合体在线粒体呼吸中起重要作用。它将电子从泛醇转移到可溶性电子穿梭细胞色素c，从而促进质子原动力穿过线粒体内膜。在酵母酿酒酵母中，每个单体由三个催化亚基和七个辅助亚基组成。在所有系统中，bc1复合物都是专一的同型二聚体。当前尚不清楚何时恰好在组装过程中发生二聚化。在这项研究中，我们确定二聚体形成是早期事件。具体而言，二聚体化是由两个Cor亚基Cor1和Cor2形成的稳定四聚体的相互作用介导的，该亚基与组装中间体II结合，后者包含完全的肝素化细胞色素b和两个小辅助蛋白Qcr7和Qcr8。细胞色素c1和Qcr6的添加可以同时发生，也可以独立于二聚化发生。这些结果揭示了组装中的严格顺序，其中二聚化发生在细胞色素b稳定辅因子获得后。最后，通过添加剩余的子单元完成组装。