Biosynthesis of Enterobacterial Common Antigen

描述：(改编自《调查员摘要》)： 本研究的目的是为了更全面地认识和理解细胞的功能。 革兰氏阴性菌的外膜及其作用机制 它的生物起源。作为实现这些目标的途径，我们调查了 肠道细菌共同抗原(ECA)合成与遗传的生化和遗传学 在大肠杆菌中组装。此外，我们还研究了它的功能。 大肠埃希菌、志贺氏志贺氏菌和鼠伤寒沙门氏菌中的ECA。 ECA是肠杆菌科特有的一种OM糖脂，它是 在这个家庭的所有成员中都存在。尽管无处不在的发生 在革兰氏阴性肠杆菌中，ECA的功能仍然存在 未知。我们之前研究ECA合成和组装的努力有 通过分离和鉴定有缺陷的突变体 这些过程。这些突变体的特征导致了 参与ECA合成的生物合成中间体的鉴定 反过来又导致了体外和体内实验的发展 在ECA组装中演示特定酶步骤的系统。不过， 非洲经委会组建工作中的几个重要步骤仍有待确定。我们 建议继续采用这种生化和遗传相结合的方法来完成 装配过程的表征。此外，我们还获得了 令人振奋的新数据有力地支持了ECA扮演着 革兰氏阴性杆菌耐药机制的重要作用 肠道细菌对胆盐的影响。因此，针对所要求的具体目标 支持期为：(1)确定非洲经委会的遗传决定因素 大肠杆菌K-12中多糖链的延长及生化 聚合机理的表征，(Ii)聚合反应的测定 大肠杆菌WEC基因簇o416在ECA组装中的作用(Iii)分离 在ECApG合成过程中存在缺陷的大肠杆菌突变株 多糖-糖苷元连接及其生化特性研究 链接形成所涉及的机制，以及(4)确定 革兰氏阴性肠杆菌对胆盐的耐受性。它是 预期这些研究将为大会提供有价值的见解 其他重要的膜糖脂和多糖。这样的信息 也将为开发新的抗菌剂提供理论依据。

DESCRIPTION: (Adapted from the Investigator's abstract): The long-term goals of this research are to gain a more complete understanding of the function of the outer membrane (OM) of gram-negative bacteria and the mechanisms involved in its biogenesis. As an approach to these goals, we have investigated the biochemistry and genetics of enterobacterial common antigen (ECA) synthesis and assembly in Escherichia coli. In addition, we have investigated the function of ECA in E. coli, Shigellaflexnerii, and Salmonella enterica serovar typhimurium. ECA is an OM glycolipid that is unique to the Enterobacteriaceae, and it is present in all members of this family. In spite of the ubiquitous occurrence of ECA in gram-negative enteric bacteria, the function of ECA has remained unknown. Our previous endeavors to study ECA synthesis and and assembly have been facilitated by the isolation and characterization of mutants defective in these processes. The characterization of these mutants has resulted in the identification of biosynthetic intermediates involved in ECA synthesis that have, in turn, led to the development of in vitro and in vivo experimental systems to demonstrate specific enzymatic steps in ECA assembly. Nevertheless, several important steps in the assembly of ECA remain to be established. We propose to continue this combined biochemical and genetic approach to complete the characterization of the assembly process. In addition, we have obtained exciting new data that strongly supports the conclusion that ECA plays an important role in the mechanism responsible for the resistance of gram-negative enteric bacteria to bile salts. Thus, the specific aims for the requested period of support are: (i) identification of the genetic determinant of ECA polysaccharide chain elongation in E. coil K-12, and biochemical characterization of the polymerization mechanism, (ii) determination of the role of o416 of the E. coli wec gene cluster in ECA assembly, (iii) isolation of E. coil mutants defective in the synthesis of the ECApG polysaccharide-aglycone linkage and biochemical characterization of the mechanism involved in linkage formation, and (iv) determination of the role of ECA in the resistance of gram-negative enteric bacteria to bile salts. It is anticipated that these studies will provide valuable insights into the assembly of other important membrane glycolipids and polysaccharides. Such information will also provide a rationale for the development of new antimicrobial agents.