Lynch Michael J, Levenson Robert, Kim Eun A, Sircar Ria, Blair David F, Dahlquist Frederick W, Crane Brian R
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106-9510, USA.
Structure. 2017 Feb 7;25(2):317-328. doi: 10.1016/j.str.2016.12.006. Epub 2017 Jan 12.
The interface between the membrane (MS) and cytoplasmic (C) rings of the bacterial flagellar motor couples torque generation to rotation within the membrane. The structure of the C-terminal helices of the integral membrane protein FliF (FliF) bound to the N terminal domain of the switch complex protein FliG (FliG) reveals that FliG folds around FliF to produce a topology that closely resembles both the middle and C-terminal domains of FliG. The interface is consistent with solution-state nuclear magnetic resonance, small-angle X-ray scattering, in vivo interaction studies, and cellular motility assays. Co-folding with FliF induces substantial conformational changes in FliG and suggests that FliF and FliG have the same stoichiometry within the rotor. Modeling the FliF:FliG complex into cryo-electron microscopy rotor density updates the architecture of the middle and upper switch complex and shows how domain shuffling of a conserved interaction module anchors the cytoplasmic rotor to the membrane.
细菌鞭毛马达的膜（MS）环与细胞质（C）环之间的界面将扭矩产生与膜内的旋转相耦合。与开关复合体蛋白FliG（FliG）的N端结构域结合的整合膜蛋白FliF（FliF）的C端螺旋结构表明，FliG围绕FliF折叠，产生一种拓扑结构，与FliG的中间和C端结构域非常相似。该界面与溶液态核磁共振、小角X射线散射、体内相互作用研究以及细胞运动性测定结果一致。与FliF共同折叠会在FliG中引起显著的构象变化，并表明FliF和FliG在转子内具有相同的化学计量比。将FliF:FliG复合体模型纳入冷冻电子显微镜转子密度中，更新了中间和上部开关复合体的结构，并展示了一个保守相互作用模块的结构域重排如何将细胞质转子锚定到膜上。
