Striker R, Jacob-Dubuisson F, Freiden C, Hultgren S J
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Biol Chem. 1994 Apr 22;269(16):12233-9.
The P pilus is a composite fiber consisting of a thin adhesive tip fibrillum joined to the pilus rod that mediates specific adherence of uropathogenic Escherichia coli to human uroepithelial cells via the PapG tip adhesin. P pilus assembly depends upon the periplasmic chaperone PapD. The interaction of PapD with different pilus subunits was investigated to gain further insight into pilus assembly. PapA, the major subunit of the pilus rod, formed two periplasmic complexes (DA2 and DA) with PapD. PapK, an adaptor protein that joins the tip fibrillum to the pilus rod, formed only one complex with PapD (DK). Only "fiber forming" or homopolymeric subunits, PapA in the rod and PapE in the tip fibrillum, were able to form subunit-subunit interactions in the periplasm. Subunits that are present in single or low copy in the pilus (PapK and PapG) did not form periplasmic intersubunit interactions. A pulse-chase analysis revealed that a chaperone-PapA complex is a true periplasmic intermediate in pilus assembly.
P菌毛是一种复合纤维，由连接到菌毛杆的细粘性尖端纤维组成，该菌毛杆通过PapG尖端粘附素介导尿路致病性大肠杆菌与人尿路上皮细胞的特异性粘附。P菌毛的组装依赖于周质伴侣蛋白PapD。研究了PapD与不同菌毛亚基的相互作用，以进一步深入了解菌毛组装。菌毛杆的主要亚基PapA与PapD形成了两种周质复合物（DA2和DA）。PapK是一种将尖端纤维连接到菌毛杆的衔接蛋白，它只与PapD形成一种复合物（DK）。只有“纤维形成”或同聚体亚基，即菌毛杆中的PapA和尖端纤维中的PapE，能够在周质中形成亚基-亚基相互作用。在菌毛中以单拷贝或低拷贝形式存在的亚基（PapK和PapG）没有形成周质亚基间相互作用。脉冲追踪分析表明，伴侣蛋白-PapA复合物是菌毛组装过程中真正的周质中间体。
