A novel lectin-independent interaction of P fimbriae of Escherichia coli with immobilized fibronectin

Binding of P fimbriae of uropathogenic Escherichia coli to purified human fibronectin and human placental type IV collagen was studied. In an enzyme immunoassay, purified P fimbriae bound strongly to immobilized intact fibronectin and to the aminoterminal 30-kDa fragment and the 120-140-kDa carboxyterminal fragments of fibronectin. Binding to the gelatin-binding 40-kDa fragment of fibronectin was considerably weaker. No binding to immobilized type IV collagen was seen. The interaction between P fimbriae and immobilized fibronectin was not inhibited by alpha-D-Gal-(1-4)-beta-D-Gal-1-O-Me, a receptor analog of P fimbriae. Moreover, a mutated P fimbria lacking the lectin activity behaved similarly in the adherence assays. Recombinant strains expressing the corresponding cloned fimbriae genes bound to immobilized fibronectin, but no binding to soluble 125I-labelled fibronectin was found. The results suggest that P fimbriae interact with immobilized fibronectin and that the binding mechanism does not involve the lectin activity of the fimbriae.