PRINCIPLES OF SENSORY RECEPTION AND MOTOR FUNCTION

本提案的重点是鼠伤寒沙门氏菌的鞭毛及其如何 它的外部零部件被导出和组装。 只有两个例外(周质P环和 外膜L环，两者都利用初级SEC分泌 途径)，外部鞭毛蛋白，如杆状蛋白，钩蛋白 蛋白质和细丝蛋白由一种专门的鞭毛输出- 特定的路径。单独的蛋白质亚基被转移到 细胞膜的平面，然后沿着中央通道向下移动 在新生的结构内，并在其远端组装。地点和方式 出口的蛋白质会穿过膜吗？尽管这个概念可能看起来 起初很奇怪，出口设备最可能的位置是在 位于基底体MS环中心的特化膜“补丁”， 它位于细胞膜上。事实上，我们最近已经展示了 其中两个出口设备组件(Flip和FLIR)是薄膜 与基体部相关的蛋白质，以及至少是 位于MS环的细胞质表面。 出口途径的已知或可疑组件--约十分之一 数字-可能分为两个或三个主要类别： 在MS环孔内形成复合体的膜蛋白， 稳定或瞬时结合的外周膜蛋白 具有作为伴侣或能源的复合体和功能 在运输过程中，和蛋白质完全驻留在 细胞质。我们希望确定(I)其他膜组件是否 的设备(FlhA、FlhB、Flio和FliQ)在物理上关联 (Ii)哪些蛋白质相互作用；(Iii) 是否存在特定需要的蛋白质来出口 给予出口的蛋白质；和(Iv)出口过程的程度(如 与组装过程相反)是有序的过程。我们也希望携带 对仪器的选定部件进行结构研究并 最终尝试在体外重建该装置。 拟议研究的重要性因以下事实而更加突出： 鞭毛输出途径和许多致病途径 细菌输出毒力因子都属于一个共同的家族，即类型 III分泌途径。

This proposal focuses on the flagellum of Salmonella typhimurium and how its external components are exported and assembled. With just two exceptions (the proteins of the periplasmic P ring and the outer membrane L ring, both of which utilize the primary Sec secretion pathway), external flagellar proteins such as the rod proteins, hook protein, and filament protein are exported by a dedicated, flagellum- specific pathway. The individual protein subunits are translocated across the plane of the cell membrane, and then travel down a central channel within the nascent structure and assemble at its distal end. Where and how do the exported proteins cross the membrane? Although the concept may seem strange at first, the most likely location for the export apparatus in a "patch" of specialized membrane at the center of the basal-body MS ring, which lies in the cytoplasmic membrane. In fact we have shown recently that two of the export apparatus components (FliP and FliR) are membrane proteins associated with the basal body and that FliR, at least, is located in the cytoplasmic face of the MS ring. The known or suspected components of the export pathway-about ten in number-are likely to fall into two or perhaps three major classes: membrane proteins that form a complex within the pore of the MS ring, peripheral membrane proteins that either stably of transiently associate with the complex and function either as chaperones or as energy sources for the transport process, and proteins that reside entirely in the cytoplasm. We hope to establish (i) whether the other membrane components of the apparatus (FlhA, FlhB, FliO, and FliQ) are physically associated with the basal body; (ii) which proteins interact with each other; (iii) whether there are proteins that are specifically required for export of a given exported protein; and (iv) to what degree the export process (as opposed to the assembly process) is an ordered one. We also hope to carry out structural studies of selected components of the apparatus and ultimately to attempt in vitro reconstitution of the apparatus. The importance of the proposed research is enhanced by the fact that the flagellar export pathway and many of the pathways by which pathogenic bacteria export virulence factors all belong to a common family, the type III secretion pathways.