Transport and Insertion of Outer Membrane Proteins

描述（由申请人提供）：革兰氏阴性菌的包膜由两层膜组成，由含有肽聚糖壁的质周隔室隔开。内膜（IM）与胞质溶胶接触，而外膜（OM）与细胞外环境接触。OM是革兰氏阴性菌必需的独特结构，由脂多糖（LPS）、磷脂和蛋白质组成。它是一种非常选择性的渗透性屏障，使细菌能够在肠道等恶劣环境中生存，在肠道中，OM对胆汁盐的抵抗力使肠道细菌茁壮成长。OM的成分在感染时首先与宿主接触，并强烈调节共生细菌和致病菌与宿主的相互作用。清楚地了解OM的生物发生过程对于理解宿主-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）是具有？-枪管结构嵌入OM。许多omp具有免疫原性，其中一些作为粘附素介导宿主组织的粘附和定植。omp在细胞质中合成，并通过Sec转运机制在IM中转运。然而，这些疏水蛋白如何穿过外周质并特异性地插入到OM中尚不清楚。许多质周伴侣和OM中的BAM复合体参与了omp的运输和插入。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）测试从结构中得出的机制假设，（iii）开发OMP转运折叠和外膜插入的综合模型。

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.