Pilus chaperone FimC-adhesin FimH interactions mapped by TROSY-NMR

The 23 kDa two-domain periplasmic chaperone FimC from Escherichia coli is required for the assembly of type-1 pili, which are filamentous, highly oligomeric protein complexes anchored to the outer bacterial membrane that mediate adhesion of pathogenic E. coli strains to host cell surfaces. Here we identified the contact sites on the surface of the NMR structure of FimC that are responsible for the binding of the 28 kDa mannose-binding type-1 pilus subunit FimH by 15N and 1H NMR chemical shift mapping, using transverse relaxation-optimized spectroscopy (TROSY). The FimH-binding surface of FimC is formed nearly entirely by the N-terminal domain, and its extent and shape indicate that FimC binds a folded form of the pilus subunits.