Functional analyses of a Listeria secretion chaperone essential for virulence

 描述(申请人提供)：革兰氏阳性细菌单核细胞增生性李斯特菌(Lm)是一种兼性细胞内病原体，依赖于各种基因产物的调节分泌和活性，以促进不同宿主环境中的生命。我们的实验室最近发现了一种名为PrsA2的蛋白质，它是一种分泌的伴侣蛋白，对肉汤培养中的细菌生长是必不可少的，但对LM的毒力是必不可少的。PrsA2是一种肽基-脯氨酰顺/反式异构酶，它有助于稳定和活性一些LM分泌的毒力因子，这些毒力因子是细菌入侵、复制和在受感染宿主内细胞间传播所必需的。我们推测，在宿主感染期间，PrsA2调节分泌蛋白的适当折叠、稳定和活性，这些蛋白有助于宿主细胞质中的细菌毒力和毒力。尽管分泌蛋白在细菌发病机制中具有关键作用，但对革兰氏阳性细菌膜转位后蛋白活性的调节机制知之甚少。其他物种中的PRSA同源物似乎是膜-细胞壁界面分泌的蛋白质因子的折叠和稳定性所必需的。Lm有两个PRSA等位基因(prsA1和prsA2)，我们已经确定了这两个等位基因之间的第一个遗传联系，一个新的双组分调控系统(Lmo1507-1508)，它同时调控prsA1和prsA2的表达。PrsA1与PrsA2有75%的氨基酸相似性和58%的同源性，我们已经解决了PrsA1的晶体结构，这是我们用来模拟PrsA2的一种新结构，以便确定两种蛋白质之间的结构变化，这些变化可能决定功能的差异。我的研究目标是从机制上确定prsA2和prsA1在LM生理和发病机制中的作用，并确定连接prsA1和prsA2的分子机制。从这些实验中获得的数据将为关键的分泌伴侣如何进行其活动和对环境信号做出反应提供新的机械性见解。

 DESCRIPTION (provided by applicant): The Gram-positive bacterium Listeria monocytogenes (Lm) is a facultative intracellular pathogen that relies on the regulated secretion and activity ofa variety of gene products to promote life within diverse host environments. Our lab recently identified a protein known as PrsA2, a secreted chaperone that is dispensable for bacterial growth in broth culture but essential for Lm virulence. PrsA2 is a peptidyl-prolyl cis/trans isomerase that contributes to the stability and activity of a number of Lm secreted virulence factors that are required for bacterial invasion, replication, and cell-to-cell spread within the infected host. We hypothesize that during host infection PrsA2 regulates the proper folding, stabilization, and activity of secreted proteins that contribute to bacterial virulence and viabiliy within the host cytosol. Despite the pivotal importance of secreted proteins in bacterial pathogenesis, little is known about the mechanisms that regulate protein activity following membrane translocation in Gram-positive bacteria. PrsA homologs in other species appear to be required for the folding and stability of secreted protein factors at the membrane-cell wall interface. Lm has two prsA alleles (prsA1 and prsA2) and we have identified the first genetic link between these two alleles, a novel two-component regulatory system (Lmo1507-1508) that regulates the expression of both prsA1 and prsA2. PrsA1 shares 75% amino acid similarity and 58% identity with PrsA2, and we have solved the crystal structure for PrsA1, a novel structure that we have used to model PrsA2 in order to identify structural changes between the two proteins that may determine functional differences. My research objectives are to mechanistically define the role of PrsA2 and PrsA1 in Lm physiology and pathogenesis and to define the molecular mechanism that links prsA1 and prsA2. Data obtained from these experiments will provide new mechanistic insight into how a critical secretion chaperone carries out its activities and is responsive to environmental signals.