The Saccharomyces cerevisiae respiratory supercomplex factor 1 (Rcf1) protein is located in the mitochondrial inner membrane where it is involved in formation of supercomplexes composed of respiratory complexes III and IV. We report the solution structure of Rcf1, which forms a dimer in dodecylphosphocholine (DPC) micelles, where each monomer consists of a bundle of five transmembrane (TM) helices and a short flexible soluble helix (SH). Three TM helices are unusually charged and provide the dimerization interface consisting of 10 putative salt bridges, defining a “charge zipper” motif. The dimer structure is supported by molecular dynamics (MD) simulations in DPC, although the simulations show a more dynamic dimer interface than the NMR data. Furthermore, CD and NMR data indicate that Rcf1 undergoes a structural change when reconstituted in liposomes, which is supported by MD data, suggesting that the dimer structure is unstable in a planar membrane environment. Collectively, these data indicate a dynamic monomer–dimer equilibrium. Furthermore, the Rcf1 dimer interacts with cytochrome c, suggesting a role as an electron-transfer bridge between complexes III and IV. The Rcf1 structure will help in understanding its functional roles at a molecular level.

在酿酒酵母呼吸超复合物因子1（Rcf1）蛋白位于线粒体内膜，参与由呼吸复合物III和IV组成的复合物的形成。我们报告了Rcf1的溶液结构，该溶液在十二烷基磷酸胆碱（DPC）胶束中形成二聚体，其中每个单体由5个跨膜（TM）螺旋束和一个短的柔性可溶螺旋（SH）束组成。三个TM螺旋带电异常，并提供由10个假定的盐桥组成的二聚化界面，定义了“电荷拉链”图案。DPC中的分子动力学（MD）模拟支持二聚体结构，尽管该模拟显示比NMR数据更动态的二聚体界面。此外，CD和NMR数据表明，Rcf1在脂质体中重构时会发生结构变化，MD数据支持了这一点，这表明二聚体结构在平面膜环境中是不稳定的。总的来说，这些数据表明动态的单体-二聚体平衡。此外，Rcf1二聚体与细胞色素相互作用c，表明它是配合物III和IV之间的电子转移桥。Rcf1结构将有助于在分子水平上了解其功能作用。