Assembly of E. coli Outer Membrane Proteins

描述（由申请人提供）：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。在异常蛋白质组装的情况下，细胞应激反应被激活，这一方面提高了其产物协助蛋白质折叠，组装和降解的基因的表达，另一方面降低了蛋白质合成以减轻组装机器的负担。这两种高度保守的互补反应的缺陷可以产生广泛的后果，从人类疾病到细菌活力和毒性的丧失。

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.