The Chemistry and Biology of Galactofuranose-Containing Glycans

项目摘要/摘要部分 棒状杆菌亚目包括许多感染源，包括致命的人类 病原体，如结核分枝杆菌。许多用于治疗结核分枝杆菌的抗生素 阻止细胞包膜组装的步骤，强调这一保护屏障的关键作用。这个 棒状杆菌的细胞膜是独一无二的，因为它是由糖和脂组成的 即使是其他细菌使用的积木也有很大的不同。其中一个 棒状杆菌细胞膜的中心特征是支原体阿拉伯半乳糖(MAG)， 其是由半乳呋喃糖(GalF)、阿拉伯呋喃糖(Araf)和 霉菌酸类。参与MAG生物合成的大多数酶都已经被鉴定出来，但当 它们在活细胞中的哪里以及如何作用来构建和重塑细胞包膜并不是 为人所知。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的变化 信封。目标1的重点是制造半乳聚糖的小分子探针--唯一的 没有有效探针的主要细胞壁成分。靶酶为UDP- 半乳糖变位酶(UGM)，它催化形成关键的构建块 生物合成必需的半乳糖。小分子探针的结果可以是 用来评估阻断半乳糖组装的后果，以了解其作用 半乳聚糖对棒状杆菌细胞膜稳定性和完整性的影响 UGM在其他生物体中的作用。目标3侧重于真菌转移酶，它构成了 细胞膜的关键真菌酸组分。这些酶的定位和 它们在细胞分裂中活动的时间尚不清楚。为了直观地显示真菌转移酶的活性 活细胞，我们建议设计荧光探针，可以精确定位Ag85的活性部位 揭示了真菌转移酶活性与细胞被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分析方法 用于实时监测和检测分枝杆菌。我们希望我们的 追求这三个目标将发现分枝杆菌防御和 棒状杆菌将导致新的抗生素策略。 重要意义： 这个应用程序的总体目标是开发新的化学探针，以了解 棒状杆菌建立并维持它们的细胞壁以生存。我们预计这将是 知识最终将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.