Binding properties of a mannose-specific lectin from the snowdrop (Galanthus nivalis) bulb

Carbohydrate binding properties of a new plant lectin (GNA) isolated from snowdrop bulbs were studied using the technique of quantitative precipitation, hapten inhibition, and affinity chromatography on immobilized lectin. Purified GNA precipitated highly branched yeast mannans but did not react with most glucans. Hapten inhibition experiments showed that D-mannose is an inhibitor of GNA-mannan interaction but neither N-acetyl-D-mannosamine nor D-glucose is an inhibitor. Hapten inhibition with various sugars showed that GNA requires the presence of equatorial hydroxyl groups at the C-3 and C-4 positions and an axial group at the C-2 position of the D-pyranose ring. A nonreducing terminal D-mannose residue is necessary for the interaction of oligosaccharides, and oligosaccharides with terminal Man(alpha-1-3)Man units showed the highest inhibitory potency (10-30 times greater than D-mannose) among the manno-oligosaccharides tested. The presence of the hydrophobic p-nitrophenyl aglycone increased the affinity of D-mannose only slightly. Immobilized GNA bound yeast mannan but did not bind glycogen. The behavior of glycoproteins with high mannose type glycan chains depended on the density and the structure of their glycan chains. Glycopeptides which carry Man(alpha 1-3)Man units were retarded on the immobilized GNA column whereas those lacking this unit or with hybrid type glycan chains were not retarded on the column.