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首页> 美国卫生研究院文献>Infection and Immunity >Lysine Residue 117 of the FasG Adhesin of Enterotoxigenic Escherichia coli Is Essential for Binding of 987P Fimbriae to Sulfatide
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Lysine Residue 117 of the FasG Adhesin of Enterotoxigenic Escherichia coli Is Essential for Binding of 987P Fimbriae to Sulfatide

机译：产肠毒素大肠杆菌的FasG黏附素的赖氨酸残基117是987P菌毛与硫化物结合所必需的

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摘要

The FasG subunit of the 987P fimbriae of enterotoxigenic strains of Escherichia coli was previously shown to mediate fimbrial binding to a glycoprotein and a sulfatide receptor on intestinal brush borders of piglets. Moreover, the 987P adhesin FasG is required for fimbrial expression, since fasG null mutants are nonfimbriated. In this study, fasG was modified by site-directed mutagenesis to study its sulfatide binding properties. Twenty single mutants were generated by replacing positively charged lysine (K) or arginine (R) residues with small, nonpolar alanine (A) residues. Reduced levels of binding to sulfatide-containing liposomes correlated with reduced fimbriation and FasG surface display in four fasG mutants (R27A, R286A, R226A, and R368). Among the 16 remaining normally fimbriated mutants with wild-type levels of surface-exposed FasG, only one mutant (K117A) did not interact at all with sulfatide-containing liposomes. Four mutants (K117A, R116A, K118A, and R200A) demonstrated reduced binding to such liposomes. Since complete phenotypic dissociation between the structure and specific function of 987P was observed only with mutant K117A, this residue is proposed to play an essential role in the FasG-sulfatide interaction, possibly communicating with the sulfate group of sulfatide by hydrogen bonding and/or salt bridge formation. Residues K17, R116, K118, and R200 may stabilize this interaction.
机译：先前已证明大肠杆菌产肠毒素菌株的987P菌毛的FasG亚基介导了仔猪肠刷缘上的糖蛋白和硫苷脂受体的纤维结合。此外，纤维蛋白表达需要987P粘附素FasG，因为fasG null突变体是无纤维的。在这项研究中，通过定点诱变对fasG进行了修饰，以研究其硫化物的结合特性。通过将带正电荷的赖氨酸（K）或精氨酸（R）残基替换为小的非极性丙氨酸（A）残基，生成了20个单个突变体。在四个fasG突变体（R27A，R286A，R226A和R368）中，与含硫酸盐的脂质体结合的水平降低与纤维化和FasG表面展示减少有关。在具有野生型水平的表面暴露FasG的16个正常残存的正常突变体中，只有一个突变体（K117A）与含硫化物的脂质体根本不相互作用。四个突变体（K117A，R116A，K118A和R200A）表现出与此类脂质体的结合减少。由于仅在突变体K117A上观察到987P的结构与特定功能之间存在完全表型解离，因此建议该残基在FasG-硫酸酯相互作用中起关键作用，可能通过氢键和/或盐与硫酸酯的硫酸根基团进行通讯桥梁形成。残基K17，R116，K118和R200可以稳定这种相互作用。

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