Cell-Wall Recycling and Nexus to Antibiotic Resistance

项目概要/摘要 细胞壁再循环是细菌中的基本过程，由此它允许在细菌中重塑细胞壁。 正常生长的过程中，并在响应抗生素，造成损害细胞壁，为他们的 行动机制。肠杆菌科和铜绿假单胞菌（本资助申请的主题） β-内酰胺类抗生素对它们细胞壁造成的感觉损伤。感知事件与细胞壁有关 再循环，这导致形成基于细胞壁的天然产物，称为尿肽。某些 胞肽被内化到细胞质中，在那里它们诱导细菌对抗生素的反应 （抗肿瘤机制）。这一过程导致许多β-内酰胺类抗生素被淘汰 对抗革兰氏阴性菌我的实验室在过去的几年里一直在研究这个系统， 在这个MIRA应用程序是路径，实验室将图表在不久的将来。我建议研究 周质复合物涉及溶解性转糖基酶（LT），其翻转细胞壁， 回收或应对抗生素的损害。我的实验室记录了P区有11个已知的LT。 铜绿假单胞菌，其与细胞壁的单独反应已经由我们描述。这些酶 被认为与周质内的其他蛋白质形成复合物，其身份尚不清楚 代表了我们对细胞壁过程的认识中的一个主要空白。然而，LT的所有功能都不是 应当理解，一种是在细菌暴露于β-内酰胺抗生素时修复细胞壁。肌肽是 细胞壁再循环的降解产物，其为此目的被内化到细胞质中。作为 作为再循环事件的分支，某些多肽在表达中激活AmpR转录调节因子， AmpC β-内酰胺酶是β-内酰胺类抗生素的耐药决定因素。我们将研究 AmpR蛋白在阐明该系统中的关键肽。此外，四个附加 已经在铜绿假单胞菌中鉴定出的胞质酶，用于胞肽的关键事件 回收将调查其化学反应，催化循环的细节， 结构.我预计，这项拟议中的科学的成功完成不仅会导致 阐明这些重要的事件调节细胞壁，而且还将确定机会， 中断作为一种手段，以规避β-内酰胺耐药的复杂机制， 细菌进化了。人们对这些复杂的事件知之甚少，我将在我的 实验室在拟议的研究过程中。

Project Summary/Abstract Cell-wall recycling is a fundamental process in bacteria, whereby it allows for remodeling of the cell wall in the course of the normal growth and in response to antibiotics that inflict damage to the cell wall for their mechanisms of action. Enterobacteriaceae and Pseudomonas aeruginosa (subject of this grant application) sense damage inflicted to their cell wall by β-lactam antibiotics. The sensing event is linked to cell-wall recycling, which leads to the formation of cell-wall-based natural products known as muropeptides. Certain muropeptides are internalized to the cytoplasm, where they induce the bacterial response to the antibiotic (antibiotic-resistance mechanisms). This process has led to obsolescence of many of the β-lactam antibiotics against Gram-negative bacteria. My lab has studied this system for the past several years and what I disclose in this MIRA application is the path that the lab will chart in the immediate future. I propose to study the periplasmic complexes involving lytic transglycosylases (LTs), which turn over the cell wall for the purpose of recycling or in response to damage by antibiotics. My lab has documented that there are 11 known LTs in P. aeruginosa, whose individual reactions with the cell wall have been described by us. These enzymes are proposed to be involved in complexes with other proteins within the periplasm, whose identities are not known and represent a major gap in our knowledge of cell-wall processes. Whereas all the functions of LTs are not understood, one is repair of cell wall upon exposure of bacteria to β-lactam antibiotics. Muropeptides are the degradation products of cell-wall recycling, which are internalized to the cytoplasm for this purpose. As an offshoot of the recycling events, certain muropetides activate the AmpR transcriptional regulator in expression of the AmpC β-lactamase, the resistance determinant for β-lactam antibiotics. We will study the interactions of the key mutropeptides with the AmpR protein in elucidating the system. Furthermore, four additional cytoplasmic enzymes that have been identified in P. aeruginosa for the key events of the muropeptide recycling will be investigated for their chemical reactions, the details of the catalytic cycles and for their structures. I anticipate that the successful completion of this proposed science will not only lead to the elucidation of these important events regulating the cell wall, but also will identify opportunities for their interruption as a means to circumventing the elaborate mechanism of β-lactam resistance that Gram-negative bacteria have evolved. These complex events are poorly understood, and they will be studied in detail in my lab in the course of the proposed reseach.