Structural and functional characterization of phosphoglycosyl transferases from human pathogens

摘要： 该项目旨在扩大对膜相关的初始步骤的机械理解， 细菌糖缀合物生物合成。膜蛋白结构在生物学中的代表性严重不足。 蛋白质数据库（PDB），并保持难以纯化，表征和机制分析的目标。 这些生物合成途径的产物是细菌生存力和毒力所必需的， 抗菌设计的有吸引力的目标。实例包括荚膜多糖（CPS）、细胞壁磷壁多糖（cellwall teichoic acid）、胞内多糖（cellular polysaccharide）、胞内多糖（cellular polysaccharide）、胞内多糖（cellular polysaccharide）。 酸、脂多糖（LPS）和N-和O-连接的糖蛋白。 糖缀合物生物合成的第一个膜结合步骤由磷酸糖基转移酶催化 （PGTs）。这类酶将糖从NDP-糖转移到十一异戊二烯磷酸脂上 锚。不同的PGTs表现出不同的底物选择性，其分子决定因素仍然存在。 未知最近，来自紧凑弯曲杆菌的PGT，PglC的第一个结构被解析，但是结晶 活性位点是开放的和未配体的构象。 苯乙烯马来酸共聚物（SMALP）和传统的洗涤剂将用于增溶和净化 不同底物选择性的PGTs。化学酶合成将用于产生UDP-糖 PGTs的底物，如UDP-二NAcBac和UDP-岩藻糖。一个快速的，基于发光的测定将是 用于表征溶解的靶标和合成的底物。脂质立方相（LCP）方法将 促进从未离开脂质双层的SMALP溶解的靶的结晶。合成基材 将用于浸泡或共结晶实验。这些实验将拓宽我们的理解 PGT结构与功能的关系。数据还将为开发抑制剂的努力提供信息，因为PGTs仍然是一种 这是开发抗微生物和抗病毒剂的一个未充分探索的领域。

Abstract: This project aims to expand the mechanistic understanding of the initial membrane-associated steps of bacterial glycoconjugate biosynthesis. Membrane protein structures are critically underrepresented in the protein data bank (PDB), and remain difficult targets for purification, characterization and mechanistic analysis. The products of these biosynthetic pathways are required for both bacterial viability and virulence and are attractive targets for antimicrobial design. Examples include capsular polysaccharide (CPS), cell wall teichoic acid, lipopolysaccharide (LPS) and N- and O-linked glycoproteins. The first membrane-bound step of glycoconjugate biosynthesis is catalyzed by phosphoglycosyl transferases (PGTs). This class of enzymes transfers a sugar from an NDP-sugar onto an undecaprenyl phosphate lipid anchor. Different PGTs exhibit different substrate selectivity, the molecular determinants of which remain unknown. The first structure of a PGT, PglC from Campylobacter concisus was solved recently, but crystallized in a conformation in which the active site is open and unliganded. Both Styrene maleic acid copolymer (SMALP) and traditional detergents will be used to solubilize and purify PGTs of differing substrate selectivity. Chemoenzymatic synthesis will be used to generate UDP-sugar substrates for PGTs such as UDP-diNAcBac and UDP-fucose. A rapid, luminescence-based assay will be used to characterize solubilized targets and synthesized substrates. Lipid cubic phase (LCP) methods will facilitate crystallization of SMALP solubilized targets that have never left a lipid bilayer. Synthetic substrates will be utilized for soaking or cocrystallization experiments. These experiments will broaden our understanding of PGT structure-function relationships. Data will also inform efforts to develop inhibitors, as PGTs remain an underexplored area for the development of antimicrobial and antivirulence agents.