ROLE OF ESCHERICHIA-COLI K-12 RFA GENES AND THE RFP GENE OF SHIGELLA-DYSENTERIAE-1 IN GENERATION OF LIPOPOLYSACCHARIDE CORE HETEROGENEITY AND ATTACHMENT OF O-ANTIGEN
ROLE OF ESCHERICHIA-COLI K-12 RFA GENES AND THE RFP GENE OF SHIGELLA-DYSENTERIAE-1 IN GENERATION OF LIPOPOLYSACCHARIDE CORE HETEROGENEITY AND ATTACHMENT OF O-ANTIGEN
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DOI：
10.1128/jb.174.22.7297-7307.1992
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发表时间：
1992-11-01
影响因子：
3.2
通讯作者：
SCHNAITMAN, CA
中科院分区：
文献类型：
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作者：
KLENA, JD;ASHFORD, RS;SCHNAITMAN, CA
对痢疾志贺菌1株的rfp基因、大肠杆菌K-12株和鼠伤寒沙门氏菌LT2株的rfA基因进行了研究，以确定它们与脂多糖核心异质性的关系及其在O抗原与脂多糖的结合中的作用。根据核苷酸序列推测，RFP基因编码一个41,864 Da的蛋白，其结构与RfaG蛋白相似。该基因在E.coliK-12中的表达导致内毒素凝胶分析中的三条带中的一条丢失，并出现一条新的、更缓慢迁移的条带。这与RFP是一种糖转移酶的假设是一致的，RFP是一种糖转移酶，它修饰核心分子的子集，使它们成为附着沙门氏菌O抗原的底物。在产生O抗原的菌株中，携带O抗原的带的凝胶迁移移动和RFP修饰带的消失表明，在附着O抗原之前，核心可能被进一步修剪或修饰。RfaL突变会导致似乎被RFP修饰的粗大内毒素条带的丢失，并阻止RFP修饰的条带的出现。因此，RfaL蛋白参与核心修饰，而不仅仅是O-抗原连接酶的一个组成部分。RfaK和rfaQ的产物似乎也参与了O抗原附着前的核心修饰，而且rfaK修饰的位置在大肠杆菌K-12和鼠伤寒沙门氏菌中是不同的。相反，RFA和RfaZ的突变会导致内毒素核心的变化，但不会影响O抗原的附着。我们认为，这些基因参与了合成粗脂多糖的另一条途径，这些粗脂多糖类似于其他物种的脂寡糖，不是O-抗原附着的底物。所有这些研究都表明，在凝胶上观察到的大肠杆菌K-12内毒素的明显异质性不是人为的，而是反映了内毒素物种之间的功能差异。
The rfp gene of Shigella dysenteriae 1 and the rfa genes of Escherichia coli K-12 and Salmonella typhimurium LT2 have been studied to determine their relationship to lipopolysaccharide (LPS) core heterogeneity and their role in the attachment of O antigen to LPS. It has been inferred from the nucleotide sequence that the rfp gene encodes a protein of 41,864 Da which has a structure similar to that of RfaG protein. Expression of this gene in E. coli K-12 results in the loss of one of the three bands seen in gel analysis of the LPS and in the appearance of, a new, more slowly migrating band. This is consistent with the hypothesis that Rfp is a sugar transferase which modifies a subset of core molecules so that they become substrates for attachment of S. dysenteriae O antigen. A shift in gel migration of the bands carrying S. dysenteriae O antigen and disappearance of the Rfp-modified band in strains producing O antigen suggest that the core may be trimmed or modified further before attachment of O antigen. Mutation of rfaL results in a loss of the rough LPS band which appears to be modified by Rfp and prevents the appearance of the Rfp-modified band. Thus, RfaL protein is involved in core modification and is more than just a component of the O-antigen ligase. The products of rfaK and rfaQ also appear to be involved in modification of the core prior to attachment of O antigen, and the sites of rfaK modification are different in E. coli K-12 and S. typhimurium. In contrast, mutations in rfaS and rfaZ result in changes in the LPS core but do not affect the attachment of O antigen. We propose that these genes are involved in an alternative pathway for the synthesis of rough LPS species which are similar to lipooligosaccharides of other species and which are not substrates for O-antigen attachment. All of these studies indicate that the apparent heterogeneity of E. coli K-12 LPS observed on gels is not an artifact but instead a reflection of functional differences among LPS species.