Glycoproteins and their derived glycopeptides have been used to define the specificity of the Lathyrus ochrus lectin and isolectins, by determining their ability to inhibit the agglutination of human erythrocytes induced by the lectin or isolectins. This α-D-mannose/α-D-glucose-specific lectin possessess the ability to recognize a well-defined saccharide sequence on a bi-antennary N-acetyllactosamine-type glycan. For other Vicieae lectins, the best inhibitor is a glycopeptide from human lactotransferrin with an α-L-fucose residue at the C-6 position on the N-acetylglucosamine residue involved in the N-glycosylamine bond. This fucose seems to be a major determinant of the binding since its removal with an α-L-fucosidase gives glycopeptides 8-fold less inhibitory. Our results confirm that the Vicieae lectins are evolutionarily related proteins even at the level of their binding sites.
