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首页> 外文期刊>Infection and immunity >Comparative Sequence Analysis of the Plasmid-Encoded Regulator of Enteropathogenic Escherichia coliStrains
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Comparative Sequence Analysis of the Plasmid-Encoded Regulator of Enteropathogenic Escherichia coliStrains

机译：肠病原性大肠杆菌菌株的质粒编码调控子的比较序列分析

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Enteropathogenic Escherichia coli (EPEC) strains that carry the EPEC adherence factor (EAF) plasmid were screened for the presence of different EAF sequences, including those of the plasmid-encoded regulator (per). Considerable variation in gene content of EAF plasmids from different strains was seen. However,bfpA, the gene encoding the structural subunit for the bundle-forming pilus, bundlin, and per genes were found in 96.8% of strains. Sequence analysis of the per operon and its promoter region from 15 representative strains revealed that it is highly conserved. Most of the variation occurs in the 5′ two-thirds of the perA gene. In contrast, the C-terminal portion of the predicted PerA protein that contains the DNA-binding helix-turn-helix motif is 100% conserved in all strains that possess a full-length gene. In a minority of strains including the O119:H2 and canine isolates and in a subset of O128:H2 and O142:H6 strains, frameshift mutations in perA leading to premature truncation and consequent inactivation of the gene were identified. Cloned perA, -B, and -C genes from these strains, unlike those from strains with a functional operon, failed to activate the LEE1 operon and bfpAtranscriptional fusions or to complement a per mutant in reference strain E2348/69. Furthermore, O119, O128, and canine strains that carry inactive per operons were deficient in virulence protein expression. The context in which the perABC operon occurs on the EAF plasmid varies. The sequence upstream of theper promoter region in EPEC reference strains E2348/69 and B171-8 was present in strains belonging to most serogroups. In a subset of O119:H2, O128:H2, and O142:H6 strains and in the canine isolate, this sequence was replaced by an IS1294-homologous sequence.
机译：筛选携带EPEC粘附因子（EAF）质粒的肠致病性大肠埃希菌（EPEC）菌株，以检查是否存在不同的EAF序列，包括质粒编码的调控子（ per ）。观察到来自不同菌株的EAF质粒的基因含量有相当大的变化。然而，在96.8％的菌株中发现了 bfpA ，该基因编码成束的菌毛，邦德林和 per 基因的结构亚基。来自15个代表性菌株的 per 操纵子及其启动子区域的序列分析表明，它是高度保守的。大多数变异发生在 perA 基因的5'三分之二处。相反，在具有全长基因的所有菌株中，包含DNA结合螺旋-转-螺旋基序的预测的PerA蛋白的C末端部分是100％保守的。在包括O119：H2和犬分离株在内的少数菌株中以及在O128：H2和O142：H6菌株的一部分中，鉴定到 perA 中的移码突变导致过早截断并导致该基因失活。 。来自这些菌株的克隆的 perA ，- B 和- C 基因与具有功能操纵子的菌株不同，它们未能激活 > LEE1 操纵子和 bfpA 转录融合体，或补充参考株E2348 / 69中的 per 突变体。此外，携带无活性的 per 操纵子的O119，O128和犬毒株在毒力蛋白表达方面缺乏。 perABC 操纵子在EAF质粒上发生的环境各不相同。在属于大多数血清群的菌株中，EPEC参考菌株E2348 / 69和B171-8中 per 启动子区域的上游序列。在O119：H2，O128：H2和O142：H6菌株的一个子集中以及犬分离株中，此序列被IS 1294 同源序列取代。

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