Assembly of E. coli Outer Membrane Proteins

描述(申请人提供)：蛋白质的组装是一个普遍的生物过程，其基本原理和机制从细菌到人类都是保守的。在蛋白质组装异常的情况下，细胞应激反应被激活，一方面提高其产物有助于蛋白质折叠、组装和降解的基因的表达，另一方面降低蛋白质合成以减轻组装机械的负担。这两种高度保守的互补反应的缺陷可能会产生广泛的后果，从人类疾病到细菌活力和毒力的丧失。 本研究研究了外膜蛋白在大肠杆菌中的组装。OMP组装分两个不同的阶段进行，第一个阶段发生在周质的可溶环境中，新生多肽在那里达到第二阶段所需的折叠状态，第二阶段发生在外膜中，在那里实现最终组装和膜插入。 更具体地说，这项拟议的研究将检查YfgL的作用，YfgL是最近发现的OMP组装机制中的一种脂蛋白成分。YfgL的缺失赋予了多效性表型，包括桶内OMP组装动力学的显著延迟，在缺乏主要周质蛋白酶DegP的背景下的条件致死性，药物超敏反应，以及在大肠杆菌和鼠伤寒沙门氏菌中毒力降低。总之，YfgL突变体的这些表型反映了YfgL在细菌生理和发病机制中广泛而重要的作用。一种新的蛋白质，YqjB，在减少包膜压力方面的作用也将被研究。假设包膜应激条件下YqjB水平升高调节EnvZ/OmpR双组分调控系统，减少OMP合成，从而缓解包膜应激。 这一建议的两个目的是为了更深入地了解可溶性OMP组装事件与发生在外膜上的OMP组装事件相协调的机制，以及相互连接的调控网络如何通过下调OMP合成来帮助降低包膜压力。 与公共健康相关：蛋白质的组装是一个普遍的生物过程，其基本原理和机制从细菌到人类都是保守的。在蛋白质组装异常的情况下，细胞应激反应被激活，一方面提高其产物有助于蛋白质折叠、组装和降解的基因的表达，另一方面降低蛋白质合成以减轻组装机械的负担。这两种高度保守的互补反应的缺陷可能会产生广泛的后果，从人类疾病到细菌活力和毒力的丧失。

DESCRIPTION (provided by applicant): The assembly of proteins is a universal biological process whose fundamental principles and machineries are conserved from bacteria to human. In the case of aberrant protein assembly, a cellular stress response is activated which, on one hand, elevates the expression of genes whose products assist in protein folding, assembly and degradation, and on the other, lowers protein synthesis to reduce the burden on the assembly machinery. Defects in these two highly conserved complementary responses can have broad consequences ranging from human diseases to loss of bacterial viability and virulence. This research investigates the assembly of ¿-barrel outer membrane proteins (OMPs) in Escherichia coli. OMP assembly proceeds in two distinct phases, the first of which occurs in the soluble environment of the periplasm where nascent polypeptides attain folding status required for the second phase that occurs in the outer membrane where the final assembly and membrane insertion are achieved. More specifically, the proposed research will examine the role of YfgL, a lipoprotein component of the recently discovered OMP assembly machinery. The absence of YfgL confers pleiotropic phenotypes, including a significant delay in ¿-barrel OMP assembly kinetics, conditional lethality in a background devoid of the major periplasmic protease DegP, drug hypersensitivity, and reduced virulence in E. coli and Salmonella typhimurium. Together, these phenotypes of YfgL mutants reflect broad and significant roles for YfgL in bacterial physiology and pathogenesis. The role of a novel protein, YqjB, in reducing envelope stress will also be examined. It is hypothesized that elevated YqjB levels under envelope stress conditions modulate the EnvZ/OmpR two-component regulatory system to reduce OMP synthesis, thereby relieving envelope stress. The two aims of this proposal are directed at gaining a deeper understanding of the mechanism by which the soluble OMP assembly events are coordinated with those that occur in the outer membrane and how the interconnected regulatory network help reduce envelope stress by down-regulating OMP synthesis. PUBLIC HEALTH RELEVANCE: The assembly of proteins is a universal biological process whose fundamental principles and machineries are conserved from bacteria to human. In the case of aberrant protein assembly, a cellular stress response is activated which, on one hand, elevates the expression of genes whose products assist in protein folding, assembly and degradation, and on the other, lowers protein synthesis to reduce the burden on the assembly machinery. Defects in these two highly conserved complementary responses can have broad consequences ranging from human diseases to loss of bacterial viability and virulence.