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）将一系列毒力相关蛋白递送到宿主细胞中引起疾病。的 这些细菌中的T3SS集中在一个称为分子注射器的复杂纳米机器上， 跨越细菌的内外膜，伸出一个丝状针状物 蛋白质进入细胞外空间。T3SS的毒力因子底物在生物化学上是 不同的，操纵宿主细胞生物系统，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 组织和系统的有益的病原体。该系统的基质被认为 以部分非球形状态行进通过分子注射器的内部通道，并且包括 在许多因素中，孔形成蛋白与针结构对接。内 在细菌中，III型分泌器具有与ATP酶相互作用并展开的ATP酶。 底物，以及促进易位的特化分泌分子伴侣。这项建议 提出了一个计划，进行晶体学研究这些毒力系统，特别是重点 关于病原体鼠伤寒沙门氏菌T3SS的三个具体方面将是 研究：（1）单个毒力因子在宿主中的功能，（2）细菌之间的相互作用 分泌伴侣及其底物，和（3）III型分泌系统的相互作用 ATP酶及其相关元件与分泌分子伴侣及其底物。晶体结构 这些元素及其生物复合物，结合后续的生物化学，细胞 生物学和感染测定，将提供重要的新见解，这一功能， 广泛而重要的毒力系统。因为细菌利用这种毒力系统， 广泛传播的人类，动物和植物疾病，了解它们如何引起疾病将 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.