Twin Ushers Guide Pili across the Bacterial Outer Membrane

The chaperone/usher pathway is responsible for the assembly of adhesive pili on the surface of gram-negative pathogenic bacteria. In this issue, present the crystal structure of the PapC usher translocation domain and images of the FimD usher bound to a pilus translocation intermediate. These new structures provide the first detailed view of a translocase in action.