SPECIFICITY OF S-FIMBRIAE ON RECOMBINANT ESCHERICHIA-COLI - PREFERENTIAL BINDING TO GANGLIOSIDES EXPRESSING NEUGC-ALPHA(2-3)GAL AND NEUAC-ALPHA(2-8)NEUAC

The adhesins of Escherichia coli strains HB101(pANN801-13) and HB101(p AZZ50), which express S fimbriae encoded by a recombinant plasmid cont aining the sfaI and sfaII gene clusters, respectively, were characteri zed with regard to the detailed structural requirements of their bindi ng to sialyloligosaccharides on (neo)glycoproteins and (neo)glycolipid s. From binding and binding inhibition studies in solid-phase enzyme i mmunoassays with isolated S fimbriae, several major conclusions can be drawn. S fimbriae bind specifically to sialic acid on gangliosides. T he most active structural variant of sialic acid on GM3 ganglioside is N-glycolylneuraminic acid (NeuGc). In contrast to previous reports, h igh binding activities were measured also for b-series gangliosides ex pressing NeuAcalpha(2-8)NeuAc. In agreement with earlier studies, the site of sialic acid substitution to subterminal sugars strongly influe nces the binding to sialyloligosaccharides, i.e., alpha-6-linked siali c acid is only poorly recognized by the adhesin compared with alpha-3- linked sialic acid. C-8 and C-9 hydroxyl groups form essential structu ral elements of sialic acid in the binding event.