Part of the yehABCD fimbrial operon. Could contribute to adhesion to various surfaces in specific environmental niches. Expression is negatively regulated by H-NS and subjected to cAMP receptor protein (CRP)-mediated catabolite repression. 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.