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. Negatively regulated by H-NS. Positively regulated by IHF and EcpR (By similarity). Mutants do not express ECP and are defective in biofilm formation. Belongs to the EcpC/MatD family.