Assembly of the mycobacterial cell wall

描述(申请人提供)：结核分枝杆菌，结核病的病原体，是成人死于传染病的主要原因。这种微生物的两个突出特征是其复杂的细胞被膜，其生物合成是几种抗生素的靶标，以及它能够在潜伏感染的个体中持续存在。抗分枝杆菌药物开发领域的主要目标包括识别细胞包膜生物合成所必需的途径，以及了解建立持久性所涉及的分子机制。在这方面，一个被该领域忽视的重要生物合成途径是肽多聚糖(PGN)组装。PGN是几乎所有细菌细胞膜的重要组成部分，为细胞提供形状和结构完整性。分枝杆菌PGN多糖是由N-酰基胞壁酸和N-乙酰氨基葡萄糖与胞壁酸部分连接的多肽(L丙氨酰或glycyl)-D-iso-glutaminyl-meso-diaminopimelyl-D-alanyl-D-丙氨酸)组成。中位二氨基甲酸(DAP)残基与D-丙氨酸或其他DAP残基之间存在多肽交联键。分枝杆菌PGN与DAP-DAP变种所代表的70%-80%的多肽和三分之一-一半的交联物高度交联。在大多数其他细菌中，DAP-DAP交联物通常只占交联物总数的几个百分点，这表明这些交联物在分枝杆菌生理学中具有重要作用。这些不寻常的交联物的生物合成和它们的功能是未知的。据认为，负责DAP-DAP交联的酶对R-内酰胺类抗生素的抑制不敏感，因此代表了一类新的靶向药物开发的酶。此外，这些联系对细胞在长期饥饿条件下的生存可能很重要。然而，还没有对任何细菌物种描述DAP-DAP连锁形成的途径。我们认为DAP-DAP连接对于分枝杆菌生理学是必不可少的，并且在稳定期生存中起作用。这些交叉链接的形成也可能是有助于建立结核病潜伏期持久性的重要机制。这项建议的总体目标是更好地了解分枝杆菌的细胞壁组装，重点是DAP-DAP交联链的生物合成和意义。了解这些交叉链接的生物学特性可能会导致开发新的抗生素来管理潜伏的结核病，这将对公共卫生产生重大影响。项目简介这项建议的总体目标是更好地了解分枝杆菌的细胞壁组装，重点是DAP-DAP交联链的生物合成和意义。了解这些交叉链接的生物学特性可能会导致开发新的抗生素来管理潜伏的结核病，这将对公共卫生产生重大影响。

DESCRIPTION (provided by applicant): Mycobacterium tuberculosis, the causative agent of tuberculosis, is the leading cause of adult death by an infectious organism. Two outstanding characteristics of this organism are its complex cell envelope the biosynthesis of which is the target of several antibiotics, and its ability to persist in latently infected individuals. Major goals of the anti-mycobacterial drug development field include the identification of pathways that are essential for cell envelope biosynthesis and understanding the molecular mechanisms involved in the establishment of persistence. In this regard, one essential biosynthetic pathway that has been overlooked in this field is peptidoglycan (PGN) assembly. The PGN is an essential component of the cell envelope of virtually all bacteria, providing both shape and structural integrity to the cell. Mycobacterial PGN polysaccharide is composed of N-acylmuramic acid and N-acetylglucosamine with peptides (L-alanyl (or glycyl)-D-iso-glutaminyl-meso-diaminopimelyl-D-alanyl-D- alanine) attached to the muramic acid moieties. Peptide cross-links occur between meso-diaminopimelic acid (DAP) residues and either D-alanine or other DAP residues. The mycobacterial PGN is highly crosslinked with 70-80% of the peptides cross-linked and one-third to one-half of the cross-links represented by the DAP-DAP variety. In most other bacteria, DAP-DAP cross-links usually represent only a few percent of the total number of cross-links, suggesting an important role for these cross-links in mycobacterial physiology. The biosynthesis of these unusual cross-links and their function are unknown. It is thought that the enzymes responsible for DAP-DAP cross-links are insensitive to inhibition by R-lactam antibiotics and thus represent a novel class of enzymes to target for drug development. Furthermore, these linkages may be important for cell survival under long-term starvation conditions. However, the pathway for DAP-DAP linkage formation has not been described for any bacterial species. We propose that DAP-DAP linkages are essential for mycobacterial physiology and have a role in stationary phase survival. The formation of these cross-links may also be an important mechanism contributing to the establishment of persistence in tuberculosis latency. The overall goal of this proposal is to better understand cell wall assembly in mycobacteria with a focus on the biosynthesis and significance of DAP-DAP cross-links. Understanding the biology of these cross-links could lead to the development of new antibiotics for the management of latent tuberculosis, which would have a significant impact upon public health. Project Narrative The overall goal of this proposal is to better understand cell wall assembly in mycobacteria with a focus on the biosynthesis and significance of DAP-DAP cross-links. Understanding the biology of these cross-links could lead to the development of new antibiotics for the management of latent tuberculosis, which would have a significant impact upon public health.