Structural Components of the Campylobacter jejuni Polar Flagellar Motor

描述(申请人提供)：鞭毛运动是许多致病菌促进宿主感染导致疾病所必需的。此外，鞭毛的运动性允许 许多环境细菌能够达到特定的生态位和营养条件，以实现最佳生长。典型的鞭毛纳米机器的结构和功能很大程度上来自于对沙门氏菌和大肠杆菌富鞭毛的累积研究。典型的鞭毛由一个从内膜和外膜延伸的鞭毛马达、一个定位于表面的钩子和一个旋转的细胞外丝组成。鞭毛马达由内膜中与鞭毛底部的转子和开关组件相联系的定子复合体和穿透肽聚糖和外膜的杆组成。定子产生离子梯度来驱动转子转动杆和灯丝，从而导致 在游泳运动中。极鞭毛细菌的鞭毛马达包含这些核心成分，但也具有对运动功能至关重要的额外结构成分。通过电子冷冻断层扫描，我们已经确定了与空肠弯曲菌极鞭毛马达相关的三个盘结构，这是美国和世界其他国家人类胃肠炎的主要原因，它们对于促进运动是必不可少的。我们已经鉴定了两种蛋白质，FlgP和Cjj0413，它们构成了这些运动盘结构中的两个。这两种蛋白质中的任何一种缺失都会使C。 空肠。由于这些蛋白质的同源物在其他极鞭毛虫中也发现，这些极鞭毛虫也产生与它们各自的鞭毛马达相关的盘状结构，我们相信我们已经确定了极鞭毛马达功能普遍需要的成分。这项建议的目标是使用空肠弯曲菌作为一个模式系统来了解鞭毛马达的结构和功能，因为它们与医学上重要的极鞭毛细菌病原体有关，如弧菌、假单胞菌和螺杆菌。在目标1中，我们将进行实验，以确定空肠弯曲菌形成运动盘结构的其他蛋白质和鞭毛运动功能特殊需要的蛋白质。在目标2中，我们将分析 基本马达盘的形成和其他马达盘成核所需的FlgP。此外，我们还将分析Cjj0413的胞质和周质结构域，以及它们对近端视盘聚合和运动性的要求。这些目标的实现将有助于理解：1)功能正常的极鞭毛马达所需的独特组件；2) 极鞭毛发动机的结构和功能的替代机制不同于 3)游动细菌之间的多样性，因为鞭毛纳米机器如何发挥作用，促进跨细菌物种的游泳运动，这对许多细菌在宿主和环境中的最佳生长至关重要。

DESCRIPTION (provided by applicant): Flagellar motility is essential for many pathogenic bacteria to promote infection of hosts to result in disease. In addition, flagellar motility allows many environmental bacteria to reach specific niches and nutrients for optimal growth. The structure and function of a prototypic flagellar nanomachine is largely derived from cumulative studies of peritrichous flagella from Salmonella species and Escherichia coli. A typical flagellum is composed of a flagellar motor that extends from the inner and outer membranes, a surface-localized hook, and an extracellular filament that rotates. The flagellar motor is composed of stator complexes in the inner membrane that associate with rotor and switch components at the base of the flagellum and a rod that penetrates the peptidoglycan and the outer membrane. The stators generate an ion gradient to power the rotor to turn the rod and the filament, which results in swimming motility. The flagellar motors of polarly-flagellated bacteria contain these core components, but also possess additional structural components that are essential for motor function. By using electron cryo-tomography, we have identified three disk structures associated with the polar flagellar motor of Campylobacter jejuni, a leading cause of gastroenteritis in humans in the United States and in other countries throughout the world, which are essential for promoting motility. We have identified two proteins, FlgP and Cjj0413, which compose two of these motor disk structures. Deletion of either protein abolishes motor function and motility in C. jejuni. Because homologues of these proteins are found in other polar flagellates that also produce disk-like structures associated with their respective flagellar motors, we believe that we have identified components universally required for function of polar flagellar motors. The objectives of this proposal are to use C. jejuni as a model system to understand construction and function of flagellar motors as they relate to medically-important polar-flagellated bacterial pathogens such as Vibrio, Pseudomonas, and Helicobacter species. In Aim 1, we will perform experiments to identify other proteins of C. jejuni forming motor disk structures and proteins specifically required for flagellar motor function. In Aim 2, we will analyze essential residues of FlgP required for formation of the basal motor disk and nucleation of the other motor disks. In addition, we will analyze cytoplasmic and periplasmic domains of Cjj0413 and their requirements for polymerization of the proximal disk and motility. Accomplishment of these aims will aid in understanding: 1) unique components required for a functional polar flagellar motor; 2) alternative mechanisms for the construction and function of polar flagellar motors that differ from peritrichous motors; and 3) diversity amongst motile bacteria for how flagellar nanomachines function to promote swimming motility across bacterial species, which is essential for optimal growth of many bacteria in hosts and in environments.