Dissecting the role of Escherichia coli peptidoglycan synthase activators

 描述（由申请方提供）：肽聚糖层（PG）是细菌细胞包膜的重要组成部分，可保护细胞免受渗透裂解。这种结构是细菌王国所独有的，使其成为许多抗生素的有价值的靶标。青霉素结合蛋白1a（PBP1a）和青霉素结合蛋白1b（PBP1b）被认为是负责PG合成的主要酶，因为它们同时失活会导致裂解。11这两种酶通过聚合聚糖链然后将这些链交联成现有的PG层来合成PG层。Bernhardt实验室目前的工作表明，某些被称为溶解性转糖基酶（LTs）的酶可能与青霉素结合蛋白（PBPs）共同作用，但这种相互作用的具体细节尚未阐明。有趣的是，LT切割聚糖链，因此我们预测细胞必须拥有一种方法来协调PBPs的活性与LT的拮抗活性。最近，发现大肠杆菌外膜脂蛋白LpoA和LpoB分别是PBP1a和PBP1b体内活性所需的。11，12然而，具有组成性过程激活剂的目的尚不清楚。该项目旨在进一步了解 通过确定LpoA和LpoB的生理作用来调节PG合成。为了实现这一目标，我将确定LpoA和LpoB的其他调节靶点，确定抑制剂，克服含有组成型活性PBP1b等位基因的菌株的细胞壁缺陷，并确定LpoA的生理功能及其激活PBP1a的机制。拟议的实验将建立在Bernhardt实验室在细菌细胞包膜生物学方面的优势基础上，并有可能揭示与未来抗生素开发相关的新生物学机制。

 DESCRIPTION (provided by applicant): The peptidoglycan layer (PG) is an essential component of the bacterial cell envelope that protects the cell from osmotic lysis. This structure is unique to the bacterial kingdom, making it a valuable target of many antibiotics. Penicillin binding protein 1a (PBP1a) and penicillin binding protein 1b (PBP1b) are thought to be the primary enzymes responsible for PG synthesis, because their simultaneous inactivation leads to lysis.11 These two enzymes synthesize the PG layer by polymerizing glycan strands and then cross-linking these strands into the existing PG layer. Current work in the Bernhardt lab suggests that certain enzymes known as lytic transglycosylases (LTs) may act in conjunction with the penicillin binding proteins (PBPs), however the specifics of this interaction are not yet elucidated. Interestingly, LTs cleave glycan strands, so we predict that cells must possess a way to coordinate the activity of PBPs with the antagonistic activity of LTs. Recently, the Escherichia coli outer membrane lipoproteins LpoA and LpoB were discovered to be required for the in vivo activity of PBP1a and PBP1b, respectively.11, 12 However, the purpose of having activators of a constitutive process is unclear. This project aims to gain further understanding of the regulation of PG synthesis by determining the physiological role of LpoA and LpoB. To accomplish this, I will identify additional regulatory targets of LpoA and LpoB, identify suppressors that overcome the cell wall defects of strains containing a constitutively active PBP1b allele, and determine the physiological function of LpoA and the mechanism of its activation of PBP1a. The proposed experiments will build on the strengths of the Bernhardt lab in bacterial cell envelope biology and have the potential to reveal novel biological mechanisms relevant to future antibiotic development.