Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin St, Houston, TX, 77030, USA.
Department of Biochemistry and Molecular Biology, McGovern Medical School, 6431 Fannin St, Houston, TX, 77030, USA.
Nat Commun. 2022 Jan 19;13(1):379. doi: 10.1038/s41467-022-28058-5.
Bacterial type IV secretion systems (T4SSs) are largely responsible for the proliferation of multi-drug resistance. We solved the structure of the outer-membrane core complex (OMCC) of a T4SS encoded by a conjugative F plasmid at <3.0 Å resolution by cryoelectron microscopy. The OMCC consists of a 13-fold symmetrical outer ring complex (ORC) built from 26 copies of TraK and TraV C-terminal domains, and a 17-fold symmetrical central cone (CC) composed of 17 copies of TraB β-barrels. Domains of TraV and TraB also bind the CC and ORC substructures, establishing that these proteins undergo an intraprotein symmetry alteration to accommodate the C13:C17 symmetry mismatch. We present evidence that other pED208-encoded factors stabilize the C13:C17 architecture and define the importance of TraK, TraV and TraB domains to T4SS function. This work identifies OMCC structural motifs of proposed importance for structural transitions associated with F plasmid dissemination and F pilus biogenesis.
细菌 IV 型分泌系统 (T4SS) 在很大程度上导致了多药耐药性的扩散。我们通过冷冻电镜解析了一个由可移动 F 质粒编码的 T4SS 的外膜核心复合物 (OMCC)，分辨率达到<3.0 Å。OMCC 由 26 个 TraK 和 TraV C 末端结构域组成的 13 重对称外环复合物 (ORC) 和由 17 个 TraB β-桶组成的 17 重对称中央锥体 (CC) 组成。TraV 和 TraB 的结构域也与 CC 和 ORC 亚结构结合，表明这些蛋白质经历了蛋白质内的对称改变，以适应 C13:C17 的对称失配。我们提供了证据表明，其他 pED208 编码的因子稳定了 C13:C17 结构，并定义了 TraK、TraV 和 TraB 结构域对 T4SS 功能的重要性。这项工作确定了 OMCC 的结构基序，这些基序可能对与 F 质粒传播和 F 菌毛生物发生相关的结构转变很重要。
