PURIFICATION AND CHARACTERIZATION OF NOVEL LECTINS FROM GREAT NORTHERN BEAN, PHASEOLUS-VULGARIS L

Two lectins, GNL-1 and 2, were isolated from extracts of Great Norther n bean powder through fractionation with ammonium sulfate, ion-exchang e chromatographies on CM- and DEAE-celluloses, and gel filtration chro matography on Sephacryl S-200 HR. These lectins were shown to be homog enous by gel electrophoresis, gel filtration, and isoelectric focusing . The lectins (GNL-1 and 2) have molecular masses of 175 and 145 kDa o n gel filtration, respectively. They yield three bands having the resp ective same molecular masses on SDS-PAGE (GNL-1; alpha-subunit of 34.5 kDa, beta of 37.0, and gamma of 39.0: GNL-2; alpha' of 34.5 kDa, beta ' of 37.0, and gamma' of 39.0). Two lectins are shown to be glycoprote ins and the carbohydrate contents of GNL-1 and 2 are 5.1 and 4.5%, res pectively. The isoelectric points are 5.5 and 5.1 and the extinction c oefficients (A1 cm1%) at 280 nm are 11.37 and 11.45, respectively. The se lectins are nonspecific in agglutination for rabbit and any types o f human erythrocytes. Inhibition study shows no specificity against mo no and disaccharides. On the other hand, binding assay of horseradish peroxidase-glycoproteins to the bands electroblotted onto PVDF membran e reveals that all of the subunits can bind to sugar moieties in fetui n, asialofetuin, and porcine thyroglobulin specifically. Moreover, ass ay of mitogenic activity shows that GNL-1 is a strong mitogen, but GNL -2 is lack of the activity.