Affinity of four immobilized Erythrina lectins toward various N-linked glycopeptides and related oligosaccharides

The behavior of N-acetyllactosamine-type oligosaccharides and glycopeptides on columns of four different Erythrina agglutinins immobilized on Sepharose was examined. The sugar-binding specificity of the four lectins is very similar and is directed toward unmasked N-acetyllactosamine sequences, the main difference between the four lectins being the relative strength of interaction of the lectins with a given glycan. Substitution of the N-acetyllactosamine sequences by sialic acid residues, either at O-3 or O-6 of galactose completely abolishes the affinity of the lectins for the saccharides. The presence of one or several alpha-Fuc-(1----3)-GlcNAc groups decreases or completely inhibits the interaction between the glycopeptides and the Erythrina lectins. Substitution of the beta-mannose residue by an additional bisecting beta-(1----4)-N-acetylglucosamine residue decreases the affinity of the lectins for these structures as compared to the unsubstituted ones. Surprisingly, the affinity of the lectins for the oligosaccharides tested is higher than for the corresponding glycopeptides. Our findings show that, after careful calibration with well-defined oligosaccharides and glycopeptides, the immobilized Erythrina agglutinin-Sepharose columns provide valuable tools for the fractionation of N-acetyllactosamine-containing oligosaccharides and glycopeptides.