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首页> 外文期刊>Journal of bacteriology >Effects of bfp Mutations on Biogenesis of Functional Enteropathogenic Escherichia coli Type IV Pili
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Effects of bfp Mutations on Biogenesis of Functional Enteropathogenic Escherichia coli Type IV Pili

机译：bfp突变对功能性肠病性大肠杆菌IV型菌毛的生物发生的影响

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Enteropathogenic Escherichia coli expresses a type IV fimbria known as the bundle-forming pilus (BFP) that is required for autoaggregation and localized adherence (LA) to host cells. A cluster of 14 genes is sufficient to reconstitute BFP biogenesis in a laboratory strain of E. coli. We have undertaken a systematic mutagenesis of the individual genes to determine the effect of each mutation on BFP biogenesis and LA. Here we report the construction and analysis of nonpolar mutations in six genes of thebfp cluster, bfpG, bfpB,bfpC, bfpD, bfpP, andbfpH, as well as the further analysis of a previously described bfpA mutant strain that is unable to express bundlin, the pilin protein. We found that mutations inbfpB, which encodes an outer membrane protein;bfpD, which encodes a putative nucleotide-binding protein; and bfpG and bfpC, which do not have sequence homologues in other type IV pilus systems, do not affect prebundlin expression or processing but block both BFP biogenesis and LA. The mutation in bfpP, the prepilin peptidase gene, does not affect prebundlin expression but blocks signal sequence cleavage of prebundlin, BFP biogenesis, and LA. The mutation in bfpH, which is predicted to encode a lytic transglycosylase, has no effect on prebundlin expression, prebundlin processing, BFP biogenesis, or LA. For each mutant for which altered phenotypes were detected, complementation with a plasmid containing the corresponding wild-type allele restored the wild-type phenotypes. We also found that association of prebundlin or bundlin with sucrose density flotation gradient fractions containing both inner and outer membrane proteins does not require any accessory proteins. These studies indicate that many bfp gene products are required for biogenesis of functional type IV pili but that mutations in the individual genes do not lead to the identification of new phases of pilus assembly.
机译：肠致病性大肠埃希菌表达一种IV型菌毛，称为成束菌毛（BFP），是自动聚集和对宿主细胞的局部粘附（LA）所必需的。由14个基因组成的簇足以重构Eem实验室菌株中的BFP生物发生。大肠杆菌。我们对各个基因进行了系统诱变，以确定每种突变对BFP生物发生和LA的影响。在这里，我们报告了 bfp 簇， bfpG ， bfpB ， bfpC 六个基因的非极性突变的构建和分析>， bfpD ， bfpP 和 bfpH ，以及对先前描述的 bfpA 突变株的进一步分析无法表达菌毛蛋白Bundlin的蛋白。我们发现， bfpB 中的突变编码一个外膜蛋白; bfpD 中编码一个假定的核苷酸结合蛋白;在其他IV型菌毛系统中没有序列同源物的 bfpG 和 bfpC 不会影响前泛素的表达或加工，但会阻断BFP生物发生和LA。 prepilin肽酶基因 bfpP 中的突变不会影响前邦德林的表达，但会阻止前邦德林的信号序列切割，BFP生物发生和LA。据预测， bfpH 中的突变编码一种溶菌性转糖基转移酶，它对前邦德林的表达，前邦德林的加工，BFP生物发生或LA没有影响。对于检测到改变的表型的每个突变体，用含有相应的野生型等位基因的质粒进行互补可以恢复野生型的表型。我们还发现，prebundlin或Bundlin与包含内膜和外膜蛋白的蔗糖密度浮选梯度级分关联，不需要任何辅助蛋白。这些研究表明功能性IV型菌毛的生物发生需要许多 bfp 基因产物，但是单个基因的突变不会导致菌毛组装新阶段的鉴定。

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