Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden.
Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden.
Biochim Biophys Acta Bioenerg. 2020 Jun 1;1861(5-6):148177. doi: 10.1016/j.bbabio.2020.148177. Epub 2020 Feb 29.
The mitochondrial bc 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 bc 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 c 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.
线粒体 bc 复合物在线粒体呼吸中起着重要作用。它将电子从泛醇转移到可溶性电子穿梭体细胞色素 c，从而有助于在内膜上产生质子动力。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。bc 复合物在所有系统中都是必需的同二聚体。目前尚不清楚二聚体形成的确切时间。在这项研究中，我们确定二聚体形成是一个早期事件。具体来说，二聚化是由两个 Cor 亚基 Cor1 和 Cor2 形成的稳定四聚体介导的，该四聚体与包含完全酰化细胞色素 b 和两个小辅助蛋白 Qcr7 和 Qcr8 的组装中间体 II 结合。细胞色素 c 和 Qcr6 的添加可以与二聚化同时发生，也可以独立于二聚化发生。这些结果揭示了组装过程中的严格顺序，其中二聚化发生在细胞色素 b 稳定获得辅因子之后。最后，通过添加其余的亚基完成组装。
