Analysis of export and membrane association of PlaB - a surface-associated phospholipase A and virulence factor of Legionella pneumophila

军团菌是细胞内病原体和军团病的病原体，军团病是一种潜在的致命肺炎。至少有18种不同的磷脂酶，包括PlaB，一种溶血性磷脂酶a，已被描述为嗜肺军团菌。最近的分析表明，plab衍生的活性促进毒力，并通过一种新的寡聚体解离机制激活。此外，尽管没有预测到信号肽，但PlaB定位于细菌表面，n端区域仍然未被切割，并且前20个氨基酸对于出口到表面不是必需的。此外，尽管没有发现跨膜结构域、β -桶结构、脂蛋白的典型特征或修饰，但PlaB与膜相关。这表明PlaB不是一个完整的，而是一个外周膜相关蛋白，迄今为止未知的与膜蛋白或脂质的相互作用完成膜关联。由于目前已知的嗜肺乳杆菌分泌模式都没有将PlaB输出到表面，我假设一种新的输出机制负责PlaB的表面呈现。在这里提出的项目中：1)嗜肺乳杆菌的决定因素和PlaB内驱动PlaB输出到表面的区域，2)负责PlaB与膜结合的相互作用因子和所涉及的各个PlaB区域，以及3)寡聚态对输出和膜结合的贡献将被分析。

Legionellae are intracellular pathogens and the causative agent of Legionnaires disease, a potentially fatal pneumonia. At least 18 different phospholipases including PlaB, a hemolytic phospholipase A, have been described for Legionella pneumophila. Recent analysis showed that PlaB-derived activity promotes virulence and is activated by a novel oligomer dissociation mechanism. Further, PlaB localizes to the bacterial surface although no signal peptide is predicted, the N-terminal region remains uncleaved, and the first 20 amino acids are not essential for export to the surface. Additionally, PlaB associates with membranes although no transmembrane domains, beta-barrel structures, typical signatures or modifications of lipoproteins have been found. This indicates that PlaB is not an integral but rather a peripheric membrane-associated protein and so far unknown interactions with membrane proteins or lipids accomplish membrane association. Since, none of the currently known secretion modes in L. pneumophila drives PlaB export to the surface, I hypothesize that a novel export mechanism is responsible for PlaB surface presentation. In the here presented project: 1) the L. pneumophila determinants and the regions within PlaB driving PlaB export to the surface, 2) interactors responsible for PlaB association with the membrane and respective PlaB regions involved, and 3) the contribution of the oligomeric state to export and membrane association will be analyzed.