PapJ is part of the Pap pilus assembly complex that plays an auxiliary role by ensuring the proper integration of PapA into the fimbrial shaft. PapA is the major shaft protein of the pilus.

1: Integrity of Escherichia coli P pili during biogenesis: properties and role of PapJ. Tennent JM, Lindberg F, Normark S; Mol Microbiol. 1990;4:747-758. PMID:1975085