Department of Biochemistry and Molecular Biology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada; Centre for Blood Research, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
Department of Biochemistry and Molecular Biology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
Structure. 2015 Jan 6;23(1):161-172. doi: 10.1016/j.str.2014.10.021. Epub 2014 Dec 18.
The type III secretion system (T3SS) is a large macromolecular assembly found at the surface of many pathogenic Gram-negative bacteria. Its role is to inject toxic "effector" proteins into the cells of infected organisms. The molecular details of the assembly of this large, multimembrane-spanning complex remain poorly understood. Here, we report structural, biochemical, and functional analyses of PrgK, an inner-membrane component of the prototypical Salmonella typhimurium T3SS. We have obtained the atomic structures of the two ring building globular domains and show that the C-terminal transmembrane helix is not essential for assembly and secretion. We also demonstrate that structural rearrangement of the two PrgK globular domains, driven by an interconnecting linker region, may promote oligomerization into ring structures. Finally, we used electron microscopy-guided symmetry modeling to propose a structural model for the intimately associated PrgH-PrgK ring interaction within the assembled basal body.
III 型分泌系统（T3SS）是一种存在于许多致病性革兰氏阴性细菌表面的大型大分子组装体。它的作用是将有毒的“效应”蛋白注入感染生物的细胞中。该大型跨膜复合物的组装的分子细节仍知之甚少。在这里，我们报告了原型鼠伤寒沙门氏菌 T3SS 的内膜成分 PrgK 的结构、生化和功能分析。我们获得了两个环构建球状结构域的原子结构，并表明 C 端跨膜螺旋对于组装和分泌不是必需的。我们还证明了由连接区驱动的两个 PrgK 球状结构域的结构重排可能促进寡聚成环结构。最后，我们使用电子显微镜引导的对称建模来提出在组装的基底体内紧密相关的 PrgH-PrgK 环相互作用的结构模型。
