BIOSYNTHESIS OF MEMBRANE GLYCOLIPIDS IN RHIZOBIUM

BB首席研究员/项目总监（最后，第一，中间）- Raetz, Christian R.H.说明应用程序的广泛、长期目标和具体目的，并参考项目与健康的关系。简要描述了本文的研究设计和实现方法。不要总结过去的成就，不要用第一人称。此描述旨在简洁准确地描述从应用程序中分离出来的b| ^ftposed work。如果^ bapplication获得资助，此描述将成为公共信息。因此，不包括ds ^专有/机密信息。DONOTEXCEED”MRPACE提供。脂多糖（lps）是组成革兰氏阴性细菌外表面的显著糖脂，包括共生生物，豆科根瘤菌。在大肠杆菌中，脂质A锚点是葡萄糖胺的六酰化双糖，在1和4'位置上含有磷酸基团。大肠杆菌生长所需的最低脂多糖包括脂质A和两种额外的糖。新出现的基因组序列表明，大肠杆菌中制造脂质A的酶存在于大多数其他革兰氏阴性菌中。脂质A（通常称为内毒素）也是引起革兰氏阴性脓毒症临床并发症的脂多糖的活性成分。脂质A结构的微小改变可对发病机制产生深远影响。一些脂质A类似物实际上是有效的内毒素拮抗剂。与大肠杆菌相比，脂质A和/？，豆科动物脂多糖是非常罕见的。豆科植物脂质A缺乏1′和4′磷酸，但在4′位置被半乳糖醛酸修饰。它与一种特殊的28碳脂肪酸酰化，并含有2-脱氧-2-氨基葡萄糖酸盐代替近端氨基葡萄糖。/?的结构，豆科植物脂多糖表明存在新的酶产生多种脂质A和核心物种。现在已经确定，脂质a1生物合成的前7种酶实际上在大肠杆菌和/？leguminosarum。差异出现在通路的后期阶段。迄今为止，被鉴定为/？豆科植物包括一个4'-磷酸酶（也是一个磷酸转移酶）、一个1-磷酸酶、一个长链酰基转移酶（带有酰基载体蛋白）和三个不同的核心糖基转移酶。表征/？leguminosarum系统应该提供对脂质A样分子功能的深入了解，包括在植物共生过程中的特殊作用，并提供创造可能具有有趣的佐剂或拮抗剂活性的新型脂质A杂交种的机会。的一些结构特征，豆荚脂质A在人类病原体中可见。嗜肺军团菌脂质A i含有C28链，而牙龈卟啉单胞菌和幽门螺杆菌脂质A缺乏4'磷酸。|在即将到来的资助期内，具体目标是：I)克隆/？leguminosarum;II)脂质4a '-磷酸酶/磷酸转移酶的分析，特别是其合成PtdIns-4-P的能力；III)测定/?中近端单位多样性的酶基础。豆荚脂质A；IV) i结合/?独特内核糖的酶的表征，豆科多糖。网站性能 ======================================== 节结束 ===========================================

BB Principal Investigator/Program Director (Last, first, Middle)- Raetz, Christian R.H. DESCRIPTION. State the application's broad, long-term objectives and specific aims, making reference to the health relatedness of the project. Describe concisely the researchdesign and methods for achieving thejMpals. Avoid summaries of past accomplishments and^kpf the first person. This description is meant to serve as a succinct and accurate description of th|^ftposed work when seperated from the application. If^Bpplication is funded, this description, as is, will become public information. Therefore,do not includS^oprietary/confidential information. DONOTEXCEED"MRPACE PROVIDED. Lipopolysaccharides (LPSs) are remarkable glycolipids that comprise the outer surfaces of Gram-negative bacteria, including the symbiotic organism, Rhizobium leguminosamm. In Escherichia coli, the lipid A anchor of LPS is a hexa-acylated disaccharide of glucosamine, bearing phosphate moieties at positions 1 and 4'. The minimal LPS required for growth of E. coli consists of lipid A and two extra sugars. Emerging genomic sequences indicate that the enzymes that make lipid A in E. coli are present in most other Gram-negative bacteria. Lipid A (often termed endotoxin) is also the active component of LPS responsible for the clinical complications of Gram-negative sepsis. Minor modifications in the structure of lipid A can have profound effects on pathogenesis. Some lipid A analogs are actually potent endotoxin antagonists. Compared to E. coli, the chemical structures of the lipid A and core domains of/?, leguminosarum LPS are very unusual. R. leguminosarum lipid A lacks the 1 and 4' phosphates, but is modified with galacturonic acid at position 4'. It is acylated with a peculiar 28 carbon fatty acid, and contains 2-deoxy-2-aminogluconate in place of the proximal glucosamine. The structure of/?, leguminosarum LPS indicates the existence of novel enzymes for generating diverse lipid A and core species. It is now established that the first seven enzymes of lipid A I biosynthesis are in fact the same in E. coli and /?. leguminosarum. The differences arise in the later stages of the pathway. To date, enzymes identified as unique to /?. leguminosarum include a 4'-phosphatase that is also a phosphotransferase, a 1-phosphatase, a long chain acyltransferase with its own acyl carrier protein, and three distinct core glycosyltransferases. Characterization of the /?. leguminosarum system should provide insights into the functions of lipid A-like molecules, including special roles during symbiosis in plants, and affords the opportunity to create novel lipid A hybrids that may have interesting adjuvant or antagonist activities. Some structural features of/?, leguminosarum lipid A are seen in human pathogens. Legionella pneumophila lipid A i contains a C28 chain, while Porphyromonas gingivalis and Helicobacter pylori lipid A lack the 4' phosphate. | In the coming grant period, the specific aims are: I) cloning of the C28 acyltransferase of/?, leguminosarum; i II) analysis of the lipid A 4'-phosphatase/phosphotransferase, especially its ability to synthesize PtdIns-4-P; III) determination of the enzymatic basis for proximal unit diversity in /?. leguminosarum lipid A; and IV) i characterization of enzymes that incorporate the unique inner core sugars of/?, leguminosarum LPS. PERFORMANCE SITE ========================================Section End===========================================