Peptidoglycan synthesis during sporulation

描述(申请人提供)：细菌的形状由细胞外的刚性结构决定和维持，该结构由肽聚糖组成，肽聚糖是一种二糖多肽单体的重复单元的聚合物。合成这些单体并将其组装成聚合物的关键酶具有很好的特性，是许多重要抗生素的靶标。然而，细胞溶解合成的单体通过细胞膜转移到其聚合位置的机制仍然是一个基本的悬而未决的问题。我们建议研究在革兰氏阳性菌枯草芽孢杆菌非必需的孢子形成过程中的易位。内孢子含有一层厚厚的肽聚糖，即孢子皮质，这在很大程度上是耐热和耐干燥的原因。孢子皮层形成所需的一个基因是孢子形成特有的，因此是两个必需基因的非必要同源基因，这两个基因编码完整的膜蛋白，在所有有细胞壁的细菌中都存在。这些基因的突变导致了细胞形状的缺陷，这与细胞壁合成中被认为的作用一致。本项目的目标是：(1)验证该蛋白在孢子形成过程中介导肽聚糖前体移位的假设；(2)鉴定包括介导细胞壁合成的蛋白在内的多蛋白复合体；以及(3)检测该蛋白和其他参与孢子肽聚糖合成的蛋白的亚细胞定位，并分析它们靶向的潜在机制。抗生素耐药细菌菌株的日益流行强调了识别潜在的新抗生素靶点的重要性，而在肽聚糖合成过程中介导前体转位的蛋白质(S)是很好的候选者。与公共卫生相关细菌感染通常用抗生素成功地治疗，抗生素是一种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产生抗药性。这项工作的目的是确定细菌的生理学方面，这些方面可能成为新抗生素的目标。公共卫生相关性我们将研究细菌构建细胞壁的过程，这种结构决定并保持它们的形状。尽管这一过程是包括青霉素在内的许多目前使用的抗生素的目标，但细菌正在迅速对这些药物产生抗药性。我们预计，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.