Purification and characterization of a lectin from seeds of the winged bean, Psophocarpus tetragonolobus (L.)DC.

A lectin from seeds of the winged bean, Psophocarpus tetragonolobus (L.)DC, has been purified to homogeneity by affinity chromatography on a Bio-Gel lactobionate adsorbent. The lectin is rich in acidic amino acids, and after isoelectric focusing in polyacrylamide gel, appeared as a single band of pI5.5 The molecular weight of the lectin is 46 000 +/- 2000 as determined by analytical ultracentrifugation. Dodecyl sulfate gel electrophoresis detected a single type of subunit with a molecular weight of 29 000 +/- 3000. The lectin has specificity for receptors containing D-galactose and agglutinates trypsinized human red blood cells of all three ABO types. Of the tested inhibitors of hemagglutination caused by winged bean lectin, p-nitrophenyl-beta-D-galactoside was the most potent. Lactose was the most active oligosaccharide tested, and other oligosaccharides containing alpha-linked D-galactose were much less inhibitory.