Transport and Insertion of Outer Membrane Proteins

描述（由申请方提供）：革兰氏阴性菌的包膜由两层膜组成，由含有肽聚糖壁的周质隔室分隔。内膜（IM）与细胞溶质接触，而外膜（OM）与细胞外环境接触。OM是革兰氏阴性菌所必需的独特结构，由脂多糖（LPS）、磷脂和蛋白质组成。它是一种非常有选择性的渗透屏障，允许细菌在恶劣的环境中生存，如肠道，其中OM对胆盐的抗性允许肠道细菌茁壮成长。OM的组分是在感染后首先与宿主接触的组分，并且强烈调节共生菌和致病菌与其宿主的相互作用。对OM生物发生过程的清楚理解对于理解宿主-病原体相互作用以及细菌生理学的基本方面是必不可少的。外膜蛋白（OMPs）是一种整合的膜蛋白，嵌入OM的桶状结构。许多外膜蛋白具有免疫原性，其中一些外膜蛋白作为粘附素介导宿主组织的粘附和定殖。外膜蛋白在胞质中合成，并通过Sec易位机制跨IM易位。然而，这些疏水蛋白如何穿过周质并特异性地插入OM中还知之甚少。OM中的许多周质伴侣和BAM复合物与OMP的运输和插入有关。在本提案中，我们将建立OMP运输和组装的机制，重点是BAM复合物。我们将（i）确定BAM复合物的结构;（ii）测试来自结构的机制假设和（iii）开发OMP运输折叠和插入外膜的综合模型。 公共卫生相关性：外膜蛋白的运输和组装是细菌生存所需的重要过程。因此，它代表了一个有吸引力的目标，为抗菌剂的发展。这些类似于β-内酰胺，其通过干扰细胞壁合成而有效。本申请旨在了解外膜蛋白运输、折叠和插入的分子机制。

DESCRIPTION (provided by applicant): 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 proces is esential to understand host- pathogen interactions as well as a fundamental aspect of bacterial physiology. Outer membrane proteins (OMPs) are integral membrane proteins with ?-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 . However, how these hydrophobic proteins cross the periplasm and insert specifically into the OM is poorly understood. A number of periplasmic chaperones and the BAM complex in the OM have been implicated in the transport and insertion of OMPs. In this proposal we will establish the mechanisms of OMP transport and assembly focusing on the BAM complex. We will (i) determine the structure of the BAM complex; (ii) test mechanistic hypotheses derived from the structures and (iii) develop an integrated model of OMP transport folding and insertion in the outer membrane. PUBLIC HEALTH RELEVANCE: Transport and assembly of outer membrane proteins is an essential process in bacteria required for viability. Therefore, it represents an attractive targetfor development of antimicrobial. These would be analogous to beta-lactams, which are effective by interfering with cell wall synthesis. This application seeks to understand the molecular mechanisms underlying outer membrane protein transport, folding and insertion.