Assembly of Eschenchia col: rfb gene products ; location and mechanisum

亚克隆、转座子插入和缺失分析表明，大肠杆菌09 rfb区约有12千碱基对。该区域编码至少7种89、74、55、50、44、41和39.5千道尔顿的多肽。对以甘露糖均聚物为0多糖的大肠杆菌08、09和克雷伯菌03、05的rfb区进行南杂交分析，结果表明大肠杆菌09的rfb区由两个区域组成，一个是所有rfb基因共有的区域，另一个是特异区域。中央特定区域的两侧是两个共同区域。大肠杆菌09 rfb突变与鼠伤寒沙门菌rfbK和rfbM的互补实验及特异性酶活性测试表明，由共同区域编码的50 kDa多肽和55 kDa多肽分别为磷酸甘露糖变性酶和gdp -甘露糖焦磷酸化酶。该区域的核苷酸序列显示，与鼠伤寒沙门氏菌相同的功能基因存在rfbK和rfbM两个基因。rfbK和rfbM编码460个氨基酸（分子量为50,809）和471个氨基酸（分子量为52,789）的蛋白质。在鼠伤寒沙门氏菌的cpsB、铜绿假单胞菌的algA、油菜黄单胞菌的xanB和沙门氏菌B、C1、C2群的rfbM基因中，甘露糖热磷酸化酶的氨基酸序列均保守。根据磷酸腺苷转氨酶基因的氨基酸特征，将其分为rfbK（09）型（rfbK（09）、rfbK（C1）、cpsG和xanA）、algC型和rfbK(B)型(rfbK(B)和rfbK（C2）三组。在这两组各自的磷酸腺苷交换酶之间没有明显的相似性。

Subcloning, transposon insertion, and deletion analyses reveal that Escherichia coli 09 rfb region is about 12 Kilobase pairs. The region encodes at least seven polypeptides of 89, 74, 55, 50, 44, 41, and 39.5 kilodaltons. Southern hybridization analysis of rfb regions of Escherichia coli 08 and 09, and Klebsiella 03 and 05, which have mannose homopolymers as their 0 polysaccharides, shows that the E.coli 09 rfb region consists of two regions, common to all these rfb genes and the specific region. The central specific region is flanked by two common regions. Complementation experiments of E.coli 09 rfb mutations with rfbK and rfbM of Salmonella typhimurium and the specific tests for the enzymatic activity show that the 50 and 55 kDa polypeptides, encoded by the common region, are phosphomannomutase and GDP-mannose pyrophosphorylase, respectively. Nucleotide sequence of the region reveals the presence of two genes, rfbK and rfbM, with respect to the same functional genes of S. typhimurium.rfbK and rfbM encode proteins of 460 amino acids (molecular weight of 50,809) and 471 amino acids (molecular weight of 52,789). The amino acid sequences of GDP-mannose pyrophosphorylase were conserved in the bacterial mannose pathway genes of cpsB of S. typhimurium, algA of Pseudomonas aeruginosa, xanB of Xanthomonas campestris, and rfbM genes of Salmonella group B, C1, and C2. From the data of amino acid identities of phosphomannomutase genes, they were classified into three groups of rfbK(09) type (rfbK(09), rfbK(C1), cpsG, and xanA), algC type, and rfbK(B)type (rfbK(B) and rfbK(C2). No striking similarity among these groups of the respective phosphomannomutase could be detected.