CopN mechanism as a key to understanding Type Three Secretion in bacteria

描述(申请人提供)：抗生素耐药性和致病性革兰氏阴性菌是一个日益重要的公共卫生问题，预计很快将超过耐甲氧西林金黄色葡萄球菌，成为细菌感染导致死亡的主要原因。尽管有明显的需求，但新抗生素的开发速度还不够快，大多数努力都涉及对现有药物的修改，而不是确定和开发新的药物靶点。对于急需的新抗生素疗法的开发，一个有吸引力的靶点是三型分泌系统(T3SS)，这是一种毒力因子输送机器，在超过25种革兰氏阴性菌(包括A、B和C类病原体)中保守。T3SS是一种多蛋白质针状机器，横跨细菌和宿主的细胞膜，将蛋白质转运体分子运送到目标细胞的膜上，并将效应分子运送到目标细胞的胞浆中。效应器通过以下方式促进毒力 利用细胞过程和颠覆宿主防御系统。虽然TTSS调节的分子机制在很大程度上是未知的，但关键的要求是毛孔是结构性关闭的，它对刺激的反应是打开的，并且分泌是一个有序的、分级的过程。 效应器通过预先形成的转运子小孔直接分泌到宿主细胞中。这个孔是由分泌的转位蛋白组成的，必须在效应器之前分泌。一种关键的调节蛋白质是堵塞毛孔的“塞子”。在Plug蛋白分泌之后，转运体被分泌，紧随其后的是效应器。在Plug蛋白缺失的菌株中，效应器被结构性地分泌，转位蛋白的分泌严重缺陷，并且这些菌株是无毒力的。重要的移位器-效应器层次结构的起源尚不清楚。我们最近已经确定了与转运体伴侣结合的插塞蛋白的第一个结构。这种结构揭示了塞子是拴在转运子上的分子支架。我们打算进一步阐明插入式移位器脚手架的作用 在多种革兰氏阴性菌中，并了解衣原体Plug蛋白的新效应功能。我们已经证明了这些具有新的微管蛋白结合功能的蛋白质，根据我们最近的结构，已经准备好确定衣原体用来调节宿主微管细胞骨架的分子策略。最后，我们将评估伴侣-转位相互作用作为广谱抗生素开发的一个新的治疗靶点。

DESCRIPTION (provided by applicant): Antibiotic resistant and pathogenic Gram-negative bacteria are an increasingly important public health concern and are expected to soon surpass methicillin-resistant S. aureus as the principal cause of mortality due to bacterial infection. Despite evident need, new antibiotics are not being developed at an adequate rate and most effort involves modifications of existing drugs, rather than identification and development of novel drug targets. An attractive target for the much-needed development of new antibiotic therapeutics is the Type Three Secretion System (T3SS), a virulence factor delivery machine that is conserved among over 25 species of Gram-negative bacteria (including category A, B, and C pathogens). The T3SS is a multi-protein needle-like machine that spans the bacterial and host membranes and delivers protein translocator molecules into the membrane of the target cell and effector molecules into the cytosol of the target cell. The effectors promote virulence by co-opting cellular processes and subverting host defenses. While the molecular mechanisms of TTSS regulation are largely unknown, key requirements are that the pore is constitutively closed, that it opens in response to a stimulus, and secretion is an orderly, hierarchical process. Effectors are secreted directly into the host cell, through a preformed translocon pore. This pore is composed of secreted translocator proteins that must be secreted prior to effectors. A key regulatory protein is the "plug" which blocks the pore. Following plug protein secretion translocators are secreted, followed by effectors. In strains where plug proteins have been deleted, effectors are secreted constitutively, translocator secretion is severely defective, and the strains are non-virulent. The origin of the essential translocator-effector hierarchy is unknown. We have recently determined the first structure of a plug protein bound to a chaperone for a translocator. This structure reveals that plugs are molecular scaffolds that are tethered to translocators. We intend to further elucidate the role of plug-translocator scaffolding in multiple gram-negative species, and to understand the novel effector function of the Chlamydial plug protein. We have shown these proteins to possess novel tubulin binding function are poised, with our recent structure, to determine the molecular strategies that Chlamydia use to regulate the host's microtubule cytoskeleton. Finally, we will evaluate the chaperone-translocator interaction as a novel therapeutic target for the development of broad-spectrum antibiotics.