Binding and precipitation of lectins from Erythrina indica and Ricinus communis (agglutinin I) with synthetic cluster glycosides.

We recently reported that tri- and tetraantennary complex type oligosaccharides with nonreducing terminal galactose residues and the triantennary asialofetuin glycopeptide can bind and precipitate certain galactose specific lectins (L. Bhattacharyya, and C.F. Brewer (1986) Biochem. Biophys. Res. Commun. 141, 963-967; L. Bhattacharyya, M. Haraldsson, and C.F. Brewer (1988) Biochemistry 27, 1034-1041). The present study investigates the binding interactions of two of these lectins, those from Erythrina indica and Ricinus communis (Agglutinin I), with mono-, bi-, and triantennary synthetic cluster glycosides, which have little structural resemblance to complex type oligosaccharides other than they possess nonreducing terminal galactose residues (R.T. Lee, P. Lin, and Y.C. Lee (1984) Biochemistry 23, 4255-4261). The enhanced affinities of the bi- and triantennary glycosides relative to the monoantennary glycoside for the two lectins are consistent with an increase in the probability of binding due to multiple binding residues in the multiantennary glycosides. The triantennary glycoside is capable of precipitating the two lectins, and quantitative precipitation data indicate that it is a trivalent ligand. The results show that the binding and precipitation activities of complex type oligosaccharides with these lectins is due solely to the presence of multiple terminal galactose residues and not to the overall structures of the oligosaccharides.