LINKER INSERTION ANALYSIS OF THE FIMH ADHESIN OF TYPE-1 FIMBRIAE IN AN ESCHERICHIA-COLI FIMH-NULL BACKGROUND

The gene encoding the Escherichia coil FimH adhesin of type 1 fimbriae has been subjected to linker insertion mutagenesis. Amino acid change s were introduced at a number of positions spanning the entire sequenc e in order to probe the structure-function relationship of the FimH pr otein, The effect of these mutations on the ability of bacteria to exp ress a D-mannose binding phenotype was assessed in a fimH null mutant (MS4) constructed by allelic exchange in the E. coli K-12 strain PC31. Mutations mapping at amino acid residues 36, 58 and 279 of the mature FimH protein were shown to completely abolish binding to D-mannose re ceptors, Differences in the level of fimbriation were also observed as a result of some of the mutations in the fimH gene. These mutants may prove useful in dissecting receptor-ligand interactions by defining r egions of the FimH protein that are important in erythrocyte binding.