Sousa Joana S, Mills Deryck J, Vonck Janet, Kühlbrandt Werner
Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany.
Elife. 2016 Nov 10;5:e21290. doi: 10.7554/eLife.21290.
Respirasomes are macromolecular assemblies of the respiratory chain complexes I, III and IV in the inner mitochondrial membrane. We determined the structure of supercomplex IIIIIV from bovine heart mitochondria by cryo-EM at 9 Å resolution. Most protein-protein contacts between complex I, III and IV in the membrane are mediated by supernumerary subunits. Of the two Rieske iron-sulfur cluster domains in the complex III dimer, one is resolved, indicating that this domain is immobile and unable to transfer electrons. The central position of the active complex III monomer between complex I and IV in the respirasome is optimal for accepting reduced quinone from complex I over a short diffusion distance of 11 nm, and delivering reduced cytochrome to complex IV. The functional asymmetry of complex III provides strong evidence for directed electron flow from complex I to complex IV through the active complex III monomer in the mammalian supercomplex.
呼吸体是线粒体内膜中呼吸链复合物I、III和IV的大分子组装体。我们通过9埃分辨率的冷冻电镜确定了来自牛心线粒体的超复合物IIIIV的结构。膜中复合物I、III和IV之间的大多数蛋白质-蛋白质接触是由多余的亚基介导的。复合物III二聚体中的两个 Rieske 铁硫簇结构域，其中一个已解析，表明该结构域是固定的，无法转移电子。呼吸体中活性复合物III单体在复合物I和IV之间的中心位置，非常适合在11纳米的短扩散距离内从复合物I接受还原型醌，并将还原型细胞色素传递给复合物IV。复合物III的功能不对称性为哺乳动物超复合物中电子从复合物I通过活性复合物III单体定向流向复合物IV提供了有力证据。
