Mechanism of Transport and Folding of Outer Membrane Proteins

革兰氏阴性细菌的包膜由两层膜组成，两层膜由 含有肽聚糖壁的周质隔间。内膜(IM) 当外膜(OM)与细胞外接触时，它与胞浆接触 环境。OM是一种独特的结构，对于革兰氏阴性细菌来说是必不可少的， 由脂多糖、磷脂和蛋白质组成。它是一个非常有选择性的 渗透性屏障，允许细菌在恶劣的环境中生存，如 肠道，OM对胆盐的抵抗力使肠道细菌茁壮成长。这个 OM的组件在感染时首先与宿主接触，并且 强烈调节共生菌和病原菌与其宿主的相互作用。一个 清楚地了解OM的生物发生过程对于了解寄主- 病原体的相互作用以及细菌生理学的一个基本方面。 外膜蛋白(Omps)是具有b-桶结构的完整膜蛋白。 嵌入在OM中的结构。许多OMP具有免疫原性，其中一些可用于 作为粘附素，介导宿主组织的黏附和定植。合成了OMP 在胞质中，并通过SEC转位机制在IM上转位 由一种称为b-Barrel的多蛋白复合体专门插入外膜 装配机(BAM)。然而，OMP的分子机制是 针对OM和由BAM插入的内容知之甚少。 在这份提案中，我们将定义OMP运输和组装的基本原理 聚焦于BAM情结。我们将(I)定义OMP针对 OM和(Ii)检验OMP插入的机制假说，该假说来自于高- BAM的拆分结构。

The envelope of Gram-negative bacteria consists of two membranes separated by the periplasmic compartment that contains the peptidoglycan wall. The inner membrane (IM) is in contact with the cytosol while the outer membrane (OM) contacts the extracellular environment. The OM is a unique structure, essential for Gram-negative bacteria, composed of lipopolysaccharide (LPS), phospholipids and proteins. It is a very selective permeability barrier that allows the bacteria to survive in hostile environments such as the gut, where the OM resistance to bile salts allows enteric bacteria to thrive. The components of the OM are the first to come in contact with a host upon infection and strongly modulate the interaction of symbiotic and pathogenic bacteria with their host. A clear understanding of the OM biogenesis process is essential to understand host– pathogen interactions as well as a fundamental aspect of bacterial physiology. Outer membrane proteins (OMPs) are integral membrane proteins with b-barrel structures embedded in the OM. Many OMPs are immunogenic and some of them serve as adhesins mediating adhesion and colonization of host tissues. OMPs are synthesized in the cytosol and translocated across the IM by the Sec translocation machinery and inserted specifically in the outer membrane by a multiprotein complex known as b-Barrel Assembly Machine (BAM). However, the molecular mechanisms by which OMPs are targeted to the OM and inserted by BAM are poorly understood. In this proposal, we will define the fundamentals of OMP transport and assembly focusing on the BAM complex. We will (i) define the mechanism of OMP targeting to the OM and (ii) test mechanistic hypotheses of OMP insertion derived from the high- resolution structures of BAM.