Tip proteins of pili associated with pyelonephritis: new candidates for vaccine development.

Escherichia coli strains associated with extra-intestinal infections frequently express carbohydrate binding adhesins which are present as minor components of pili. The adhesin protein, PapG, and at least two other minor pilus subunits, PapE and PapF, are associated with the tips of Gal alpha (1-4)Gal-binding Pap pili or P fimbriae of uropathogenic E. coli. The structural and antigenic variation of these tip-associated proteins is discussed and evidence is presented showing that serologically identical pili may contain antigenically distinct adhesins each capable of binding to a specific receptor. One approach to the purification of these tip-associated proteins is presented and involves complex formation with the periplasmic transport protein PapD.