Institute of Structural Molecular Biology, Birkbeck and University College London, London, UK.
Adv Exp Med Biol. 2011;715:159-74. doi: 10.1007/978-94-007-0940-9_10.
Among bacteria, the chaperone-usher (CU) pathway is a widespread conserved assembly and translocation system for adhesive protein fibres, called pili or fimbriae. Pili are large linear polymers that protrude from the outer bacterial surface and consist of several subunits. Pili contain adhesin proteins at the tip that are used by pathogenic bacteria to mediate attachment to host cells and initiate infections. Well studied examples of CU pili are P and type 1 pili of uropathogenic Escherichia coli (UPEC), which are responsible for kidney and bladder infections, respectively. Upon secretion into the periplasm, pilus subunits are stabilized by periplasmic chaperones and the resulting chaperone:subunit complexes are guided to the usher located in the outer membrane. The usher catalyzes the ordered assembly of pilus subunits while releasing the chaperones and translocating the growing pilus stepwise to the outer surface. Here we review the structural biology of the chaperone-usher pathway that has helped to understand the mechanisms by which biogenesis of an important class of bacterial organelles occurs.
在细菌中，伴侣蛋白- usher (CU) 途径是一种广泛保守的组装和转运系统，用于将粘性蛋白纤维（称为菌毛或纤毛）。菌毛是从细菌外表面突出的大型线性聚合物，由几个亚基组成。菌毛的尖端含有粘附蛋白，致病性细菌利用这些蛋白与宿主细胞结合并引发感染。研究得比较透彻的 CU 菌毛的例子是尿路致病性大肠杆菌 (UPEC) 的 P 菌毛和 1 型菌毛，它们分别负责肾脏和膀胱感染。菌毛亚基在分泌到周质后，由周质伴侣蛋白稳定，并将形成的伴侣蛋白：亚基复合物引导至位于外膜的 usher。 usher 催化菌毛亚基的有序组装，同时释放伴侣蛋白，并将生长中的菌毛逐步转运到外表面。在这里，我们综述了伴侣蛋白- usher 途径的结构生物学，这有助于理解一类重要的细菌细胞器生物发生的机制。
