Biosynthesis of Enterobacterial Common Antigen

描述：（改编自研究者摘要）：长期目标 这项研究是为了更全面地了解 革兰氏阴性菌外膜（OM）及其相关机制 它的生物起源。为了实现这些目标，我们研究了 肠细菌共同抗原（ECA）合成的生物化学和遗传学， 在大肠杆菌中组装。此外，我们还研究了 ECA在E.大肠杆菌、福氏志贺菌和鼠伤寒沙门氏菌。 ECA是肠杆菌科特有的OM糖脂， 存在于这个家庭的所有成员中。尽管普遍存在的 ECA在革兰氏阴性肠道菌中，ECA的功能一直保留 未知我们以前的努力，研究ECA的合成和组装， 通过分离和表征缺陷的突变体， 这些过程。这些突变体的特征导致了 鉴定涉及ECA合成的生物合成中间体， 反过来，又导致了体外和体内实验的发展， 系统来证明ECA组装中的特定酶促步骤。然而，尽管如此， 非洲经委会的几个重要步骤尚待确定。我们 我建议继续这种生物化学和遗传学相结合的方法， 组装过程的表征。此外，我们还获得了 令人兴奋的新数据有力地支持了ECA发挥作用的结论， 在革兰氏阴性杆菌耐药机制中的重要作用 肠道细菌转化为胆盐。因此，所要求的具体目标 支持期间的主要任务是：（i）确定ECA的遗传决定因素 多糖链的延长。coil K-12和生化 聚合机理的表征，（ii）聚合反应的 o416的作用。ECA组装中的大肠杆菌wec基因簇，（iii）分离 大肠ECApG合成缺陷的卷曲突变体 多糖-糖苷配基连接和生物化学表征 参与联系形成的机制，以及（iv）确定 ECA在革兰氏阴性肠道菌对胆盐耐药性中的作用。是 预计这些研究将为大会提供宝贵的见解 其他重要的膜糖脂和多糖。此类信息 也将为开发新的抗菌剂提供理论基础。

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.