The long-term goal of the application is to understand the role of enterobacterial adhesins in the colonization of extra-intestinal habitats. The proposed study is designed to clarify the molecular mechanism by which mannose-sensitive type 1 fimbriae of Escherichia coli mediate development of urinary tract infection. Receptor specificity of the fimbrial adhesive protein, FimH, will be characterized based on it's interaction with defined saccharide receptors in soluble and immobilized forms. The relationship between the type 1 fimbrial phenotypes and the primary structure of FimH adhesins will be determined by site-directed mutagenesis of the polymorphic and conserved amino acid residues of FimH. The molecular basis of the different binding properties of FimH variants will be defined based on the functional characteristics of fimbriae-incorporated and purified forms of FimH and by using rabbit antibodies against different FimH regions. The role of the different FimH variants in colonization of vaginal introitus with E. coli will be investigated by defining the type 1 fimbrial phenotype of the vaginal isolates and, also, of the matching fecal and urinary clones. Ability of the type 1 fimbriae to mediate E. coli adhesion to human vaginal epithelial cells and secretion compounds will be tested. The comparative study of FimH variants proposed will contribute to general understanding of the adaptive evolution of enterobacterial pathogens within extra-intestinal compartments of the human organism. Such information may be useful in optimizing methods to prevent dissemination of pathogens from the human gut.