P-FIMBRIAE OF UROPATHOGENIC ESCHERICHIA-COLI AS MULTIFUNCTIONAL ADHERENCE ORGANELLES

P fimbriae are the major single virulence factor of uropathogenic Esch erichia coli strains. Recent analyses have shown that P fimbriae posse ss two distinct binding specificities mediated by different fimbrial s ubunits. P fimbriae bind to Galalpha(1-4)Gal-containing globoseries of glycolipids of epithelial cells; this binding is mediated by the lect in-like minor protein G of the filament. In vitro mapping of the human urinary tract for binding sites of P fimbriae has revealed that they bind in a Galalpha(1-4)Gal-inhibitable manner to epithelia of kidney a nd bladder. On the other hand, P fimbriae bind to immobilized fibronec tin and its amino- and carboxyterminal fragments; this binding is depe ndent on the E and the F minor proteins of the P-fimbrial filament and seems to be based on a protein-protein interaction. The P fimbriae - fibronectin interaction has been demonstrated also on frozen sections of kidney. P fimbriae thus possess two tissue-adherence properties: on e specific for epithelial glycoconjugates and the other for fibronecti n of subepithelial extracellular matrices. P-fimbrial binding to epith elial glycoconjugates seems to be important in determining the host tr opism and enabling the ascent of E. coli urinary tract infections. Bin ding to fibronectin may be important in secondary phases of the infect ion, e.g. after epithelial injury.