Molecular Targets in Peptidoglycan Synthesis

肽聚糖合成中的分子靶标

• 批准号: 7012727
• 负责人: Christopher Davies
• 金额: $ 18.71万
• 依托单位: MEDICAL UNIVERSITY OF SOUTH CAROLINA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7012727
• 关键词: Escherichia coli; Neisseria gonorrhoeae; beta lactam antibiotic; binding proteins; carbohydrate biosynthesis; drug resistance; immunopharmacology; intermolecular interaction; penicillins; peptidases; peptidoglycan; protein biosynthesis

DESCRIPTION (provided by applicant): The murein sacculus is a mesh of cross-linked peptidoglycan strands that confers rigidity to the bacterial cell wall. Beta-lactam antibiotics, which target the essential transpeptidases (penicillin-binding proteins or PBPs) that cross-link the peptidoglycan strands, are important compounds in the treatment of bacterial diseases. Unfortunately, the emergence of multiple mechanisms of antibiotic resistance threatens to make these and other antibiotics obsolete in the treatment of bacterial infections. Along with other pathogenic bacteria, antibiotic resistance in Neisseria gonorrhoeae is a growing problem. Penicillin and tetracycline, once the antibiotics of choice for treatment of gonococcal infections, are no longer be used due to the emergence of resistant strains. Moreover, increasing numbers of strains are now resistant to the fluoroquinolones, one of the two antibiotics current recommended in the treatment of gonorrhea. Clearly there is an urgent need to develop new antimicrobials directed both against well-known molecular targets, such as PBPs, but also against novel targets. In this proposal we describe structural and biochemical studies of three enzymes involved in peptidoglycan metabolism: a D-D-carboxypeptidase from E. coli (PBP 5) that serves as a model system for elucidating PBP function, an essential transpeptidase (PBP 2) from N. gonorrhoeae that is the lethal target of current beta-lactam antibiotics, and a lytic transglycosylase, MltA, also from N. gonorrhoeae, that serves as the lynchpin of the cell wall synthesizing complex. Each of these proteins has been selected to address one or more of the following aims: (a) to understand the biology of peptidoglycan synthesis, (b) to explore their interactions with antibiotics, (c) to elucidate the molecular basis for antibiotic resistance and (d) to examine their potential as targets for drug development. Studies on PBP 5 will elucidate the mechanism by which this enzyme hydrolyzes substrate and will provide a better understanding of PBP-antibiotic interactions in general. The molecular basis for antibiotic resistance in PBP 2 will be investigated by structural studies of the native enzyme and of a mutant isolated from a penicillin-resistant strain. The role of MltA as part of a multienzyme complex mediating peptidoglycan synthesis as well as its suitability as a novel target for antimicrobials will be examined by solving its crystal structure. These studies will provide a framework for future studies aimed at structure-based drug design and will provide substantial insight into the mechanisms of peptidoglycan synthesis.

描述（由申请人提供）：壁球囊是交联肽聚糖链的网状结构，赋予细菌细胞壁刚性。 β-内酰胺抗生素以交联肽聚糖链的必需转肽酶（青霉素结合蛋白或 PBP）为目标，是治疗细菌性疾病的重要化合物。 不幸的是，多种抗生素耐药机制的出现可能会使这些抗生素和其他抗生素在细菌感染的治疗中过时。与其他致病菌一样，淋病奈瑟菌的抗生素耐药性是一个日益严重的问题。青霉素和四环素曾经是治疗淋球菌感染的首选抗生素，但由于耐药菌株的出现而不再使用。此外，越来越多的菌株现在对氟喹诺酮类药物产生耐药性，氟喹诺酮类药物是目前推荐用于治疗淋病的两种抗生素之一。显然，迫切需要开发新的抗菌药物，既针对众所周知的分子靶点，如 PBP，又针对新靶点。在本提案中，我们描述了参与肽聚糖代谢的三种酶的结构和生化研究：来自大肠杆菌的 D-D-羧肽酶 (PBP 5)，作为阐明 PBP 功能的模型系统，来自大肠杆菌的必需转肽酶 (PBP 2)。淋球菌是当前 β-内酰胺类抗生素的致命目标，而裂解性转糖基酶 MltA 也来自淋球菌。淋病菌，作为细胞壁合成复合体的关键。选择这些蛋白质中的每一种是为了解决以下一个或多个目标：（a）了解肽聚糖合成的生物学，（b）探索它们与抗生素的相互作用，（c）阐明抗生素耐药性的分子基础，以及(d) 检查它们作为药物开发目标的潜力。对 PBP 5 的研究将阐明该酶水解底物的机制，并将提供对 PBP-抗生素相互作用的一般更好的理解。 PBP 2 抗生素耐药性的分子基础将通过对天然酶和从青霉素耐药菌株中分离出的突变体的结构研究来研究。 MltA 作为介导肽聚糖合成的多酶复合物的一部分的作用及其作为抗菌药物新靶点的适用性将通过解析其晶体结构来检查。这些研究将为未来基于结构的药物设计研究提供框架，并将为肽聚糖合成机制提供深入的见解。