Part of the yadCKLM-htrE-yadVN fimbrial operon. Could contribute to adhesion to various surfaces in specific environmental niches. Repressed by H-NS. Induced by heat shock. Deletion of the operon under classical laboratory conditions does not result in any major effect on E.coli capacity to form biofilms compared with the wild-type strain. The operon is cryptic under classical laboratory conditions, but is functional when constitutively expressed. Belongs to the periplasmic pilus chaperone family. Was originally called ecpD, but ecp is now used for the ecpABCDE operon involved in E.coli common pilus (ECP) synthesis.