Department of Biochemistry, University of Oxford, Oxford, UK.
FEMS Microbiol Rev. 2014 Jul;38(4):802-22. doi: 10.1111/1574-6976.12061. Epub 2014 Feb 17.
Many bacteria that live in contact with eukaryotic hosts, whether as symbionts or as pathogens, have evolved mechanisms that manipulate host cell behaviour to their benefit. One such mechanism, the type III secretion system, is employed by Gram-negative bacterial species to inject effector proteins into host cells. This function is reflected by the overall shape of the machinery, which resembles a molecular syringe. Despite the simplicity of the concept, the type III secretion system is one of the most complex known bacterial nanomachines, incorporating one to more than hundred copies of up to twenty different proteins into a multi-MDa transmembrane complex. The structural core of the system is the so-called needle complex that spans the bacterial cell envelope as a tripartite ring system and culminates in a needle protruding from the bacterial cell surface. Substrate targeting and translocation are accomplished by an export machinery consisting of various inner membrane embedded and cytoplasmic components. The formation of such a multimembrane-spanning machinery is an intricate task that requires precise orchestration. This review gives an overview of recent findings on the assembly of type III secretion machines, discusses quality control and recycling of the system and proposes an integrated assembly model.
许多生活在真核宿主接触的细菌，无论是共生体还是病原体，都进化出了操纵宿主细胞行为的机制，以使其受益。一种这样的机制，即 III 型分泌系统，被革兰氏阴性细菌物种用来将效应蛋白注入宿主细胞。该机制的整体形状类似于分子注射器，反映了其功能。尽管概念简单，但 III 型分泌系统是已知最复杂的细菌纳米机器之一，将多达一百多个不同的蛋白质之一到二十多种整合到一个多兆道尔顿的跨膜复合物中。该系统的结构核心是所谓的针复合物，它跨越细菌细胞膜作为一个三分体环系统，并以从细菌细胞表面突出的针结束。底物靶向和易位是通过由各种内膜嵌入和细胞质成分组成的出口机制来完成的。形成这样的多膜跨越机制是一个复杂的任务，需要精确的协调。这篇综述概述了 III 型分泌机器组装的最新发现，讨论了系统的质量控制和回收，并提出了一个综合的组装模型。
