Structural Studies of Bacterial Virulence Factors

大量医学上重要的细菌病原体利用III型蛋白分泌系统 (T3SS)将毒力相关蛋白的武器库输送到宿主细胞中导致疾病。这个 这些细菌中的T3SS集中在一个复杂的纳米机器上，称为分子注射器 横跨细菌的内膜和外膜，突出丝状针状物 蛋白质进入细胞外空间。T3SS的毒力因子底物是生化的 不同的、可操纵的宿主细胞生物系统，如细胞骨架结构、信号转导、 细胞周期进程和程序性细胞死亡，使细菌能够精确地调节宿主 有利于病原体的组织和系统。该系统的底物被认为是 以部分非球状状态通过分子注射器的内通道，并且包括 在许多因素中，形成毛孔的蛋白质与针状结构对接。在 细菌，III型分泌器具有与之相互作用并展开的ATPase 底物，以及促进易位的专门分泌伴侣。这项建议 提出了一项对这些毒力系统进行结晶学研究的计划，尤其是 关于病原菌鼠伤寒沙门氏菌。T3SS的三个具体方面将是重点 研究：(1)单个毒力因子在宿主中的作用；(2)细菌之间的相互作用 分泌伴侣及其底物；(3)III型分泌系统的相互作用 与分泌伴侣及其底物有关的ATPase和相关元件。晶体结构 这些元素及其生物复合体，结合后续的生化，细胞 生物学和感染分析将为这一功能提供重要的新见解 广泛而重要的毒力系统。因为利用这种毒力系统的细菌会导致 广泛传播的人类、动物和植物疾病，了解它们是如何导致疾病的 为改善公共卫生提供重要工具。

A large number of medically important bacterial pathogens utilize a type III protein secretion system (T3SS) to deliver an arsenal of virulence-associated proteins into host cells to cause disease. The T3SS in these bacteria are centered on an intricate nano-machine termed a ¿molecular syringe¿ that spans both the inner and out membranes of the bacterium, projecting a filamentous needle-like protein into the extra-cellular space. The virulence factor substrates of T3SS are biochemically diverse, manipulating host cell biological systems such as cytoskeletal structure, signal transduction, cell cycle progression, and programmed cell death, allowing bacteria to precisely modulate host tissues and systems for the benefit of the pathogen. The substrates of the system are thought to travel in a partially non-globular state through the inner channel of the molecular syringe, and include among many factors pore forming proteins with which the needle structure docks. Within the bacterium, the type III secretion apparatus possesses an ATPase that interacts with and unfolds substrates, as well as specialized secretion chaperones that promote translocation. This proposal presents a plan to conduct crystallographic studies of these virulence systems, focused particularly on the pathogen Salmonella typhimurium. Three specific aspects of the T3SS will be the focus of the study: (1) individual virulence factor function in the host, (2) the interactions between bacterial secretion chaperones and their substrates, and (3) the interaction of the type III secretion system ATPase and associated elements with secretion chaperones and their substrates. Crystal structures of these elements and their biological complexes, in combination with follow-up biochemical, cell biological, and infection assays, will provide significant new insight into the functioning of this widespread and important virulence system. Because bacteria utilizing this virulence system cause widespread human, animal, and plant disease, this understanding how they cause disease will provide important tools for improving public health.