Peptidoglycan synthesis during sporulation

描述（由申请人提供）：细菌形状由肽聚糖（二糖肽单体重复单元的聚合物）组成的细胞外刚性结构决定和维持。合成这些单体并将其组装成聚合物的必需酶已得到很好的表征，并且是许多重要抗生素的靶标。然而，胞质合成的单体跨细胞质膜易位到其聚合位点的机制仍然是一个基本的未解决的问题。我们建议调查易位过程中的非必要的过程中的芽孢形成革兰氏阳性菌枯草芽孢杆菌。内生孢子含有一层厚的肽聚糖，孢子皮层，这是其耐热和抗干燥的主要原因。孢子皮层形成所需的一个基因是孢子形成特异性的，因此是编码在所有具有细胞壁的细菌中发现的整合膜蛋白的两个必需基因的非必需同源物。这些基因的突变导致细胞形状的缺陷，这与细胞壁合成中的作用一致。本项目的目的是：（1）检验该蛋白质在孢子形成过程中介导肽聚糖前体易位的假设;（2）表征多蛋白复合物，包括介导细胞壁合成的蛋白质;（3）检查该蛋白质和其他参与孢子肽聚糖合成的蛋白质的亚细胞定位，并分析其靶向的潜在机制。抗生素耐药菌株的日益流行强调了鉴定潜在的新抗生素靶标的重要性，并且在肽聚糖合成期间介导前体易位的蛋白质是极好的候选物。与公共卫生的相关性细菌感染通常用抗生素成功治疗，抗生素是干扰细菌生长和繁殖能力的药物。然而，越来越多的细菌对这些药物有抗药性。这项工作的目的是确定可能成为新抗生素靶点的细菌生理学方面。我们将研究细菌构建细胞壁的过程，细胞壁的结构决定并保持其形状。尽管这一过程是目前使用的许多抗生素（包括青霉素）的目标，但细菌正在迅速对这些药物产生耐药性。我们希望对这一过程的新理解将导致新抗生素的开发。

DESCRIPTION (provided by applicant): Bacterial shape is determined and maintained by an extracellular, rigid structure composed of peptidoglycan, a polymer of repeated units of a disaccharide peptide monomer. The essential enzymes that synthesize these monomers and assemble them into polymers are well characterized and are the targets of many important antibiotics. However, the mechanism by which the cytosolically synthesized monomers are translocated across the cytoplasmic membrane to their site of polymerization remains a fundamental unresolved issue. We propose to investigate translocation during the non-essential process of sporulation in the Gram-positive bacterium Bacillus subtilis. The endospore contains a thick layer of peptidoglycan, the spore cortex, which is largely responsible for its heat and desiccation resistance. One gene required for spore cortex formation is a sporulation-specific and therefore non-essential homolog of two essential genes that encode integral membrane proteins found in all bacteria with a cell wall. Mutations in these genes lead to defects in cell shape consistent with a proposed role in cell wall synthesis. The objectives of this project are: (1) to test the hypothesis that this protein mediates translocation of the peptidoglycan precursor during sporulation; (2) to characterize the multiprotein complexes including the protein that mediate cell wall synthesis; and (3) to examine the subcellular localization of this protein and other proteins involved in spore peptidoglycan synthesis and analyze the underlying mechanisms responsible for their targeting. The increasing prevalence of strains of antibiotic-resistant bacteria emphasizes the importance of identifying potential new antibiotic targets and the protein(s) that mediate precursor translocation during peptidoglycan synthesis are excellent candidates. Relevance to Public Health Bacterial infections are usually treated successfully with antibiotics, drugs that interfere with the ability of the bacteria to grow and multiply. However, an increasing number of bacteria are resistant to these drugs. The aim of this work is to identify aspects of the physiology of the bacteria that might become the targets of new antibiotics. PUBLIC HEALTH RELEVANCE We will study the process by which bacteria construct their cell wall, the structure that determines and maintains their shape. Although this process is the target of many presently used antibiotics including penicillin, bacteria are quickly becoming resistant to these drugs. We expect that new understanding of this process will lead to the development of new antibiotics.