School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
J Biol Chem. 2012 Mar 16;287(12):9072-80. doi: 10.1074/jbc.M111.300624. Epub 2012 Jan 17.
The type II secretion system of Gram-negative bacteria is important for bacterial pathogenesis and survival; it is composed of 12 mostly multimeric core proteins, which build a sophisticated secretion machine spanning both bacterial membranes. OutC is the core component of the inner membrane subcomplex thought to be involved in both recognition of substrate and interaction with the outer membrane secretin OutD. Here, we report the solution structure of the HR domain of OutC and explore its interaction with the secretin. The HR domain adopts a β-sandwich-like fold consisting of two β-sheets each composed of three anti-parallel β-strands. This structure is strikingly similar to the periplasmic region of PilP, an inner membrane lipoprotein from the type IV pilus system highlighting the common evolutionary origin of these two systems and showing that all the core components of the type II secretion system have a structural or sequence ortholog within the type IV pili system. The HR domain is shown to interact with the N0 domain of the secretin. The importance of this interaction is explored in the context of the functional secretion system.
革兰氏阴性菌的 II 型分泌系统对细菌的发病机制和生存至关重要；它由 12 个主要的多聚体核心蛋白组成，这些蛋白构建了一个复杂的分泌机器，跨越细菌的内外膜。OutC 是内膜亚基复合物的核心组成部分，被认为参与了底物的识别和与外膜分泌蛋白 OutD 的相互作用。在这里，我们报告了 OutC 的 HR 结构域的溶液结构，并探索了它与分泌蛋白的相互作用。HR 结构域采用 β-三明治样折叠，由两个 β-片层组成，每个 β-片层由三个反平行的 β-链组成。这种结构与 PilP 的周质区域非常相似，PilP 是来自 IV 型菌毛系统的一种内膜脂蛋白，突出了这两个系统的共同进化起源，并表明 II 型分泌系统的所有核心成分在 IV 型菌毛系统中都有结构或序列的同源物。结果表明，HR 结构域与分泌蛋白的 N0 结构域相互作用。在功能性分泌系统的背景下，探讨了这种相互作用的重要性。
