Evolutionary and functional relationships of colonization factor antigen I and other class 5 adhesive fimbriae of enterotoxigenic Escherichia coli
Evolutionary and functional relationships of colonization factor antigen I and other class 5 adhesive fimbriae of enterotoxigenic Escherichia coli
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DOI：
10.1128/iai.72.12.7190-7201.2004
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发表时间：
2004-12-01
影响因子：
3.1
通讯作者：
Savarino, SJ
中科院分区：
文献类型：
--
作者：
Anantha, RP;McVeigh, AL;Savarino, SJ
定殖因子抗原I（CFA/I）是肠毒素大肠杆菌（ETEC）的8种遗传相关菌毛的原型，称为5类菌毛。这些细胞器由交替的伴侣蛋白途径组装而成，包括一个由聚合的主要亚基和一个明显位于尖端的次要粘附亚基组成的刚性柄。我们研究了5类特异性结构蛋白的进化关系，并将其与功能特性相关联。我们测序了编码大肠杆菌表面抗原4（CS4），CS 14，CS 17，CS 19和推定的定植因子抗原O 71（PCFO 71）的基因簇，并分析了推导的蛋白质和已发表的CFA/I，CS 1和CS2的同源物。每个操纵子编码的蛋白质的多重比对和系统发育分析定义了三个亚类，5a（CFA/I，CS4和CS 14），5 b（CS 1，CS 17，CS 19和PCFO 71）和5c（CS2）。它们与其他三个属的菌毛系统有着遥远的进化关系。亚类划分通常与区分携带ETEC菌毛的菌株的体外粘附表型相关。个体结构蛋白的系统发育比较表明，较小亚基之间的亚类内保守性大于主要亚基。为了将其与功能属性相关联，我们制备了针对CFA/I和CS 17全菌毛和麦芽糖结合蛋白融合物的抗体，其具有相应次要亚基的氨基末端一半。抗次要亚基Fab制备物显示出对表达同源和亚类内异源定植因子的ETEC的血凝抑制（HAI），而抗菌毛Fab组分显示出仅限于定植因子同源ETEC的HAI活性。这些结果与Caco-2细胞粘附试验的类似结果相证实。我们的研究结果表明，第5类菌毛的次要亚单位可能是上级诱导抗粘附免疫的整个菌毛。
Colonization factor antigen I (CFA/I) is the archetype of eight genetically related fimbriae of enterotoxigenic Escherichia coli (ETEC) designated class 5 fimbriae. Assembled by the alternate chaperone pathway, these organelles comprise a rigid stalk of polymerized major subunits and an apparently tip-localized minor adhesive subunit. We examined the evolutionary relationships of class 5-specific structural proteins and correlated these with functional properties. We sequenced the gene clusters encoding coli surface antigen 4 (CS4), CS14, CS17, CS19, and putative colonization factor antigen O71 (PCFO71) and analyzed the deduced proteins and the published homologs of CFA/I, CS1, and CS2. Multiple alignment and phylogenetic analysis of the proteins encoded by each operon define three subclasses, 5a (CFA/I, CS4, and CS14),5b (CS1, CS17, CS19, and PCFO71), and 5c (CS2). These share distant evolutionary relatedness to fimbrial systems of three other genera. Subclass divisions generally correlate with distinguishing in vitro adherence phenotypes of strains bearing the ETEC fimbriae. Phylogenetic comparisons of the individual structural proteins demonstrated greater intrasubclass conservation among the minor subunits than the major subunits. To correlate this with functional attributes, we made antibodies against CFA/I and CS17 whole fimbriae and maltose-binding protein fusions with the amino-terminal half of the corresponding minor subunits. Anti-minor subunit Fab preparations showed hemagglutination inhibition (HAI) of ETEC expressing homologous and intrasubclass heterologous colonization factors while anti-fimbrial Fab fractions showed HAI activity limited to colonization factor-homologous ETEC. These results were corroborated with similar results from the Caco-2 cell adherence assay. Our findings suggest that the minor subunits of class 5 fimbriae may be superior to whole fimbriae in inducing antiadhesive immunity.