Mechanism of Transport and Folding of Outer Membrane Proteins

革兰氏阴性菌的包膜由两层膜组成， 包含肽聚糖壁的周质区室。内膜（IM） 当外膜（OM）接触细胞外基质时，外膜与细胞质接触。 环境OM是一种独特的结构，对革兰氏阴性菌至关重要， 由脂多糖（LPS）、磷脂和蛋白质组成。这是一个非常有选择性的 渗透屏障，允许细菌在恶劣的环境中生存， 在肠道，OM对胆盐的抗性允许肠道细菌茁壮成长。的 OM的组分在感染后首先与宿主接触， 强烈调节共生菌和致病菌与宿主的相互作用。一 清楚地了解有机质的生物发生过程对于了解宿主是至关重要的， 病原体相互作用以及细菌生理学的基本方面。 外膜蛋白（Outer membrane proteins，OMPs）是一种具有b-barrel结构的膜蛋白 嵌入OM的结构。许多外膜蛋白具有免疫原性，其中一些 作为介导宿主组织的粘附和定殖的粘附素。OMPs合成 在胞质溶胶中，并通过Sec易位机制跨IM易位， 通过一种多蛋白复合物b-Barrel特异性地插入外膜 装配机（BAM）。然而，OMP的分子机制是 针对OM并由BAM插入的目标知之甚少。 在本提案中，我们将定义OMP运输和组装的基本原理 专注于军火市场我们将（i）界定外地办事处的机制， OM和（ii）测试OMP插入的机制假设来自高- BAM的解析结构。

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.