Abstract
SummaryTypes 1 and P pili are prototypical bacterial cell-surface appendages playing essential roles in mediating adhesion of bacteria to the urinary tract. These pili, assembled by the chaperone-usher pathway, are polymers of pilus subunits assembling into two parts: a thin, short tip fibrillum at the top, mounted on a long pilus rod. The rod adopts a helical quaternary structure and is thought to play essential roles: its formation may drive pilus extrusion by preventing backsliding of the nascent growing pilus within the secretion pore; the rod also has striking spring-like properties, being able to uncoil and recoil depending on the intensity of shear forces generated by urine flow. Here, we present an atomic model of the P pilus generated from a 3.8 Å resolution cryo-electron microscopy reconstruction. This structure provides the molecular basis for the rod’s remarkable mechanical properties and illuminates its role in pilus secretion.
Highlights
Chaperone-usher (CU) pili are ubiquitous appendages displayed on the surface of bacterial pathogens (Thanassi et al, 1998)
During donor-strand exchange’’ (DSE), the donor strand provided by the chaperone to complement the subunit fold is replaced by another subunit’s N-terminal extension (Nte), a 10–20 residue extension found at the N terminus of each subunit except the subunit located at the very tip
Assembly is recruited to the N-terminal domain (NTD); (2) this positions the Nte of the incoming subunit next to the groove of the subunit located at the C-terminal domains (CTDs); (3) DSE occurs, leading to the nascent pilus length increasing by one subunit and leading to the dissociation of the chaperone in the chaperone:subunit complex located at the CTDs; (4) the CTDs site is free, and the nascent pilus can transfer from the NTD to the CTDs
Summary
Hospenthal, Adam Redzej, Karen Dodson, ..., Frank DiMaio, Edward H. An atomic model of the P pilus rod generated from a 3.8 Aresolution cryoEM reconstruction provides the molecular basis for its remarkable mechanical properties that allow bacteria to maintain adhesion to the urinary tract. Highlights d The atomic structure of a chaperone-usher pilus rod was solved by cryo-EM.
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