Organization and function of a type II secretion complex

II型分泌（T2S）系统的细胞外分泌和靶向递送被认为是革兰氏阴性病原体的主要毒力机制，因为通过T2S途径分泌的许多蛋白质构成了重要的毒力因子，包括毒素和降解酶。T2S装置由至少13种不同的蛋白质EpsC-EpsN和PilD组成，它们组装成一个跨越霍乱弧菌整个细胞膜的复合体。这种复合物的动态和短暂性可能是其功能的先决条件，因为它的组装和拆卸可能驱动细胞外分泌。这个过程所需的能量被认为是由EpsE水解ATP产生的，EpsE是一种细胞质蛋白，通过与膜蛋白EpsL的相互作用与细胞质膜相关。EpsM和EpsF。EpsE与这些成分的相互作用调节其atp酶活性，并促进其定位到霍乱弧菌细胞包膜内的不同位点。

Extracellular secretion and targeted delivery by the type II secretion (T2S) system is considered a major virulence mechanism in gram negative pathogens, as many of the proteins secreted via the T2S pathway constitute important virulence factors, including toxins and degradative enzymes. The T2S apparatus is comprised of at least 13 different proteins, EpsC-EpsN and PilD, that assemble into a complex that spans the entire cell envelope of Vibrio cholerae. The dynamic and perhaps transient nature of this complex may be a prerequisite for function as its assembly and disassembly may drive extracellular secretion. The energy required for this process is thought to be generated from ATP hydrolysis by EpsE, a cytoplasmic protein that is associated with the cytoplasmic membrane via interaction with the membrane proteins EpsL. EpsM and EpsF. EpsE's interactions with these components modulate its ATPase activity and promote its localization to distinct sites within the V. cholerae cell envelope. The experiments described in this proposal are designed to test the hypothesis that specific protein-protein interactions and acidic phospholipids drive T2S in an ATP-dependent process at discrete sites In the cell envelope of V. cho/erae. Specffically, this proposal will i) determine the mechanism by which the enzymatic activity of EpsE is controlled by components of the cytoplasmic membrane including phospholipids. EpsL and EpsF; ii) investigate the ordered assembly of Eps components and determine the mechanism by which EpsD and EpsC drive focal assembly of the T2S complex; iii) map the cleft that forms when EpsM assembles and identify the cellular factor that binds to the cleft. Resolving the mechanisms of regulated assembly and spatial localization of the T2S system will further our understanding of T2S and may identify ways to manipulate the secretion process for preventative, therapeutic and/or biotechnological use.