Spreter Thomas, Yip Calvin K, Sanowar Sarah, André Ingemar, Kimbrough Tyler G, Vuckovic Marija, Pfuetzner Richard A, Deng Wanyin, Yu Angel C, Finlay B Brett, Baker David, Miller Samuel I, Strynadka Natalie C J
Department of Biochemistry and Molecular Biology and the Center for Blood Research, University of British Columbia, Vancouver, Canada.
Nat Struct Mol Biol. 2009 May;16(5):468-76. doi: 10.1038/nsmb.1603. Epub 2009 Apr 26.
The type III secretion system (T3SS) is a macromolecular 'injectisome' that allows bacterial pathogens to transport virulence proteins into the eukaryotic host cell. This macromolecular complex is composed of connected ring-like structures that span both bacterial membranes. The crystal structures of the periplasmic domain of the outer membrane secretin EscC and the inner membrane protein PrgH reveal the conservation of a modular fold among the three proteins that form the outer membrane and inner membrane rings of the T3SS. This leads to the hypothesis that this conserved fold provides a common ring-building motif that allows for the assembly of the variably sized outer membrane and inner membrane rings characteristic of the T3SS. Using an integrated structural and experimental approach, we generated ring models for the periplasmic domain of EscC and placed them in the context of the assembled T3SS, providing evidence for direct interaction between the outer membrane and inner membrane ring components and an unprecedented span of the outer membrane secretin.
III型分泌系统（T3SS）是一种大分子“注射体”，它使细菌病原体能够将毒力蛋白转运到真核宿主细胞中。这种大分子复合物由跨越细菌两层膜的相连环状结构组成。外膜分泌蛋白EscC的周质结构域和内膜蛋白PrgH的晶体结构揭示了构成T3SS外膜环和内膜环的三种蛋白质中模块化折叠的保守性。这导致了这样一种假设，即这种保守的折叠提供了一种共同的环构建基序，使得能够组装出T3SS特有的大小可变的外膜环和内膜环。我们采用综合的结构和实验方法，生成了EscC周质结构域的环模型，并将其置于组装好的T3SS环境中，为外膜环和内膜环组件之间的直接相互作用以及外膜分泌蛋白前所未有的跨度提供了证据。
