The Chemistry and Biology of Galactofuranose-Containing Glycans

项目概要/摘要部分 棒状杆菌亚目包括许多传染性病原体，包括致命的人类病原体。 病原体，如结核分枝杆菌（M. tb）。许多抗生素用于治疗M。TB 在细胞包膜组装的块步骤，强调这一保护屏障的关键作用。的 棒状杆菌的细胞被膜是由糖和脂质组成的 甚至与其他细菌所使用的构建模块也有很大不同。之一 棒状杆菌族细胞包膜的中心特征是分枝菌酰阿拉伯半乳聚糖（mAG）， 其是由呋喃半乳糖（Galf）、阿拉伯呋喃糖（Araf）和 分枝菌酸大多数参与mAG生物合成的酶已经被鉴定， 它们在活细胞中的位置以及如何构建和重塑细胞包膜， 知道的为了阐明这些变化及其功能作用，拟议的目标侧重于 开发新的工具来探测、干扰和利用棒状杆菌细胞中的变化 信封.目标1的重点是产生半乳聚糖的小分子探针-唯一的 主要细胞壁成分，不存在有效的探针。目标酶是UDP- 吡喃半乳糖苷（UGM），它催化关键构件的形成 必需的半乳聚糖的生物合成所需的。所得到的小分子探针可以 用于评估阻断半乳聚糖组装的后果，以了解 半乳聚糖在棒状杆菌科细胞被膜稳定性和完整性中的作用，并探讨 UGM在其他生物体中的作用。目的3集中在分枝菌酰转移酶，其构建了 细胞被膜的关键分枝菌酸成分。这些酶的定位和 它们在细胞分裂中的活性时间是未知的。为了使分枝菌酰转移酶活性在 活细胞，我们建议设计荧光探针，可以精确定位Ag 85活动的网站 并揭示了分枝菌酰转移酶活性和细胞包膜组装之间的相互作用。我们 预期目标3中描述的探针可用于开发寻找抑制剂的测定法 以及用于真实的实时监测和检测分枝杆菌。我们希望我们 追求这三个目标将揭示分枝杆菌防御的弱点， 棒状杆菌，这将导致新的抗生素策略。 重要性： 本申请的总体目标是开发新的化学探针，以了解 棒状杆菌类构建并维持它们细胞壁以生存。我们预计， 知识将最终导致确定治疗传染病的新战略。

Project Summary/Abstract Section The Corynebacterineae suborder encompasses many infectious agents, including deadly human pathogens, such as Mycobacterium tuberculosis (M. tb). Many antibiotics used to treat M. tb block steps in cell envelope assembly, underscoring the key role of this protective barrier. The Corynebacterineae cell envelope is unique in that it is constructed from saccharide and lipid building blocks that differ dramatically even from those used by other bacteria. One of the central features of the Corynebacterineae cell envelope is the mycolyl arabinogalactan (mAG), which is a glycoconjugate assembled from galactofuranose (Galf), arabinofuranose (Araf), and mycolic acids. Most enzymes involved in mAG biosynthesis have been identified but when, where, and how they function in live cells to construct and remodel the cell envelope is not known. To elucidate these changes and their functional roles, the proposed aims focus on developing new tools to probe, perturb, and exploit changes in the Corynebacterineae cell envelope. The focus of Aim 1 is on generating a small molecule probe of the galactan—the only major cell wall constituent for which no effective probes exist. The target enzyme is UDP- galactopyranose mutase (UGM), which catalyzes the formation of the key building block required for biosynthesis of the essential galactan. The small molecule probe that results can be used to evaluate the consequences of blocking galactan assembly to understand the role of galactan in the stability and integrity of the cell envelope in Corynebacterineae and to probe the role of UGM in other organisms. Aim 3 focuses on the mycolyltransferases, which construct the critical mycolic acid components of the cell envelope. The localization of these enzymes and the timing of their activity in cell division is not known. To visualize mycolyltransferase activity in live cells, we propose to devise fluorogenic probes that can pinpoint the sites of Ag85 activity and reveal the interplay between mycolyltransferase activity and cell envelope assembly. We anticipate that the probes described in Aim 3 can be used to develop assays for finding inhibitors of cell division and for monitoring and detecting mycobacteria in real time. We expect that our pursuit of the three aims shall uncover vulnerabilities in the defenses of mycobacteria and corynebacteria that will lead to new antibiotic strategies. Significance: The overall objective of this application is to develop new chemical probes to understand how the Corynebacterineae build and maintain their cell wall to survive. We anticipate that this knowledge will lead ultimately to the identification of new strategies to treat infectious disease.