Maturation of Bacterial Cell Wall

描述(申请人提供)：细菌的生存取决于其细胞壁的健康状况。由于细胞壁的不可缺少的性质，其组装的生物合成酶和细胞壁本身是几种现有抗生素的靶标。细胞壁组装和成熟的最后步骤是由一组被称为青霉素结合蛋白(PBPS)的酶在细胞质膜表面进行的。顾名思义，这些酶被β-内酰胺类抗生素(例如青霉素)抑制，它们是这些抗生素杀菌活性的有效靶标。尽管它们很重要，但多溴联苯类化合物的许多生化方面还没有被研究过，目前还没有其他已知的有效的抑制剂来抑制这些酶。这个项目在三个具体目标的范围内解决了这一信息匮乏的问题。特定目标1处理具有DD转肽酶活性的多氯联苯。这些酶执行细胞壁的重要的交联反应。这些研究建立在Mobashery实验室早期的工作基础上，通过实验和计算分析阐明了酶反应中的微观步骤。这些知识被应用于基于机制的抑制这些酶的策略。具体目标2将通过实验和计算解决具有DD-羧基肽酶活性的多溴联苯的机理细节。这些酶对细胞壁进行水解性处理，从而缓和DD转肽酶执行的交联度。具体目标3阐述了具有转糖基酶和DD转肽酶活性的双功能多酚的催化机制，明确地探索了两个活性部位之间的串扰，这两个活性部位将在细胞壁的生物合成中相互影响。

DESCRIPTION (provided by applicant): Survival of the bacterium depends on the health of its cell wall. Because of the indispensable nature of the cell wall, the biosynthetic enzymes of its assembly and the cell wall itself are targets of several of the existing antibiotics. The final steps of cell wall assembly and maturation are performed by a group of enzymes referred to as penicillin- binding proteins (PBPs) on the surface of the cytoplasmic membrane. As the name suggests, these enzymes are inhibited by beta-lactam antibiotics (e.g., penicillins), and they serve as validated targets for the bactericidal activity by these antibiotics. Despite their importance, many aspects of biochemistry of PBPs have not been investigated and there are currently no other known effective inhibitors for these enzymes. This project addresses this paucity of information within the scope of three Specific Aims. Specific Aim 1 deals with PBPs with the DD-transpeptidase activity. These enzymes perform the important cross-linking reaction of the cell wall. The studies build on earlier work from the Mobashery lab in elucidation of the microscopic steps in the enzymic reaction, both by experiments and by computational analyses. The knowledge is applied to a strategy for mechanism-based inhibition of these enzymes. Specific Aim 2 will address the mechanistic details of PBPs with the DD-carboxypeptidase activity by both experiments and computation. There enzymes process the cell wall hydrolytically, whereby they moderate the degree of cross-linking that is performed by DD-transpeptidases. Specific Aim 3 addresses the catalytic mechanisms of bifunctional PBPs that possess the transglycosylase and DD-transpeptidase activities, explicitly exploring the cross-talk between the two active sites that would influence one another in biosynthesis of cell wall.