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首页> 外文期刊>Infection and immunity >The structural gene encoding human enterotoxigenic Escherichia coli PCFO20 is homologous to that for porcine 987P.
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The structural gene encoding human enterotoxigenic Escherichia coli PCFO20 is homologous to that for porcine 987P.

机译：编码人肠毒素性大肠杆菌PCFO20的结构基因与猪987P同源。

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Putative colonization factor PCFO20 was recently identified in an enterotoxigenic Escherichia coli (ETEC) strain of serogroup O20 isolated from a child with diarrhea in Argentina. The gene encoding the structural subunit of PCFO20 fimbriae, fotA, was cloned from strain ARG-2 in the expression phage vector lambda ZAP Express. One positive clone, pGV29, that carried a 3.3-kb fragment was identified on the basis of fimbrillin production by using a monospecific rabbit anti-PCFO20 serum. Nucleotide sequencing of a 1.3-kb Sau3A-ClaI fragment of the subclone pGV292 containing the region coding for PCFO20 fimbrillin revealed two open reading frames of which one was complete. A western blot (immunoblot) showed that the cloned protein, FotA, migrated like the PCFO20 fimbrial subunit protein did. Fimbriae were not detected on the surface of E. coli host bacteria containing pGV292 or pGV29, suggesting that the genes needed for assembly of PCFO20 fimbriae are lacking in both clones. The fotA gene encodes a 20,574-Da prefimbrillin protein which contains a 21-amino-acid signal sequence; the mature protein has a size of 18.1 kDa. The subunit protein FotA was found to be more homologous to the subunit of porcine 987P than to any fimbrial subunit produced by human ETEC. Alignments of the amino acid sequences of the two proteins indicate that they are partly identical, with an overall similarity of 82%. FotA fimbrillin was shown to be transported and assembled by the fimbria assembly machinery in porcine ETEC strain 987. PCFO20 and 987P may have evolved from a common ancestral gene. They are immunologically related but have affinity for different host cell receptors, since PCFO20-producing bacteria do not bind to neonatal piglet enterocytes.
机译：最近在阿根廷腹泻儿童中分离出的O20血清群的产肠毒素大肠埃希氏菌（ETEC）菌株中鉴定出推定的定植因子PCFO20。从表达噬菌体载体λZAP Express的ARG-2株克隆了编码PCFO20菌毛的结构亚基fotA的基因。通过使用单特异性兔抗PCFO20血清，根据菌毛蛋白的产生，鉴定了一个带有3.3kb片段的阳性克隆pGV29。对包含编码PCFO20菌毛蛋白区域的pGV292亚克隆的1.3 kb Sau3A-ClaI片段进行核苷酸测序，发现有两个完整的阅读框。蛋白质印迹（免疫印迹）表明，克隆的蛋白FotA像PCFO20纤维亚基蛋白一样迁移。在含有pGV292或pGV29的大肠杆菌宿主细菌表面未检测到菌毛，这表明两个克隆均缺少组装PCFO20菌毛所需的基因。 fotA基因编码20,574-Da的前纤毛蛋白，其中包含21个氨基酸的信号序列。成熟蛋白质的大小为18.1 kDa。发现亚基蛋白FotA与猪987P的亚基比与人ETEC产生的任何纤维亚基更同源。两种蛋白质的氨基酸序列比对表明它们部分相同，总体相似性为82％。已显示FotA纤毛蛋白是由菌毛组装机器在猪ETEC菌株987中运输和组装的。P​​CFO20和987P可能是从一个共同的祖先基因进化而来的。它们具有免疫学相关性，但对不同的宿主细胞受体具有亲和力，因为产生PCFO20的细菌不与新生仔猪肠上皮细胞结合。

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