Interaction between pap-encoded pilin and adhesin gene products of uropathogenic Escherichia coli

Uropathogenic Escherichia coli are major causative agents of cystitis and pyelonephritis. Most E. coli pyelonephritis isolates express pili encoded by the pyelonephritis-associated pili (pap) gene cluster. The pap DNA sequence encodes pilin monomers that are assembled into pili fibers; pap also encodes adhesins that recent results suggest might be located at the tips of the pilus fibers. The study presented here is a status report of work that has two major goals: to determine (1) if any Pap proteins associate with pili and (2) if Pap proteins not required for pili assembly affect levels of pili-cell surface expression. To address the first aim, antisera to pili were used to precipitate pili from detergent extracts containing 35S-labeled Pap proteins. The results suggested that a protein of 16-kilodaltons apparent molecular mass associated with pili. Other interpretations of the data are discussed. The second aim was addressed by constructing E. coli strains that contained different pap regions. With the use of electron microscopy and a pili ELISA, it was found that E. coli containing a 6.5-kilobase-pair region of pap expressed low levels of pili, but no P-adhesin was detected. Transformation of this E. coli strain with a plasmid containing an additional 3.5-kilobase-pair pap DNA sequence resulted in an eightfold increase in pili expression as well as expression of P adhesin. These results indicated that pili expression was affected by Pap proteins not required for pili assembly.