The differential affinity of the usher for chaperone-subunit complexes is required for assembly of complete pili
The differential affinity of the usher for chaperone-subunit complexes is required for assembly of complete pili
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DOI：
10.1111/j.1365-2958.2010.07089.x
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发表时间：
2010-04-01
影响因子：
3.6
通讯作者：
Thanassi, David G.
中科院分区：
文献类型：
--
作者：
Li, Qinyuan;Ng, Tony W.;Thanassi, David G.
通过粘附性表面结构附着到宿主细胞上是许多细菌致病的先决条件。尿路致病性大肠杆菌装配P和1型皮利以附着于宿主尿路上皮。这些皮利的组装需要保守的伴侣蛋白/引导蛋白途径，其中周质伴侣蛋白控制菌毛亚基的折叠，外膜引导蛋白为菌毛组装和分泌提供平台。引导员对菌毛亚基具有不同的亲和力，对尖端定位的粘附素具有最高的亲和力。在这里，我们确定残基F21和R652的P菌毛usher PapC作为功能的差异亲和力的usher。R652对于与粘附素的高亲和力结合是重要的，而F21对于限制PapA主要杆亚基的亲和力是重要的。这些残基中的PapC突变体在PapA存在下对于菌毛组装是特异性缺陷的，表明引导子的差异亲和力是完整皮利组装所需的。PapG缺失突变体的分析表明，粘附素是不需要启动P菌毛生物合成。因此，引导器的不同亲和力对于确保功能性菌毛纤维的组装可能是至关重要的。
P>Attachment to host cells via adhesive surface structures is a prerequisite for the pathogenesis of many bacteria. Uropathogenic Escherichia coli assemble P and type 1 pili for attachment to the host urothelium. Assembly of these pili requires the conserved chaperone/usher pathway, in which a periplasmic chaperone controls the folding of pilus subunits and an outer membrane usher provides a platform for pilus assembly and secretion. The usher has differential affinity for pilus subunits, with highest affinity for the tip-localized adhesin. Here, we identify residues F21 and R652 of the P pilus usher PapC as functioning in the differential affinity of the usher. R652 is important for high-affinity binding to the adhesin whereas F21 is important for limiting affinity for the PapA major rod subunit. PapC mutants in these residues are specifically defective for pilus assembly in the presence of PapA, demonstrating that differential affinity of the usher is required for assembly of complete pili. Analysis of PapG deletion mutants demonstrated that the adhesin is not required to initiate P pilus biogenesis. Thus, the differential affinity of the usher may be critical to ensure assembly of functional pilus fibres.