Handover mechanism of the growing pilus by the bacterial outer-membrane usher FimD.

Pathogenic bacteria such as Escherichia coli assemble surface structures termed pili, or fimbriae, to mediate binding to host-cell receptors. Type 1 pili are assembled via the conserved chaperone-usher pathway. The outer-membrane usher FimD recruits pilus subunits bound by the chaperone FimC via the periplasmic N-terminal domain of the usher.

The Escherichia coli P and Type 1 Pilus Assembly Chaperones PapD and FimC Are Monomeric in Solution.

Unlabelled: The chaperone/usher pathway is used by Gram-negative bacteria to assemble adhesive surface structures known as pili or fimbriae. Uropathogenic strains of Escherichia coli use this pathway to assemble P and type 1 pili, which facilitate colonization of the kidney and bladder, respectively. Pilus assembly requires a periplasmic chaperone and outer membrane protein termed the usher.

The pilus usher controls protein interactions via domain masking and is functional as an oligomer.

The chaperone-usher (CU) pathway assembles organelles termed pili or fimbriae in Gram-negative bacteria. Type 1 pili expressed by uropathogenic Escherichia coli are prototypical structures assembled by the CU pathway. Biogenesis of pili by the CU pathway requires a periplasmic chaperone and an outer-membrane protein termed the usher (FimD).