Part of the ecpRABCDE operon, which encodes the E.coli common pilus (ECP). ECP is found in both commensal and pathogenic strains and plays a dual role in early-stage biofilm development and host cell recognition. Tip pilus adhesin, which is required for assembly of EcpA into fibers (By similarity). Forms polymers. Interacts with EcpA. Negatively regulated by H-NS. Positively regulated by IHF and EcpR (By similarity). Not expressed under classical laboratory conditions, but is functional when constitutively expressed. Belongs to the EcpD/MatE family.