PURIFICATION, PHYSICOCHEMICAL CHARACTERIZATION AND BIOLOGICAL PROPERTIES OF A LECTIN FROM ERYTHRINA-VELUTINA FORMA AURANTIACA SEEDS

A lectin was purified from seeds of Erythrina velutina forma aurantiac a by affinity chromatography on cross-linked guar gum. The lectin is a potent agglutinin for human (minimal concentration of protein able to cause visible agglutination of a 2% erythrocyte suspension varying fr om 1 to 4 mu g/ml), rabbit (4 mu g/ml) and chicken erythrocytes (8 mu g/ml) but presented low activity against cow (250 mu g/ml) or sheep (3 33 mu g/ml) blood cells. Hemagglutination of human O+ erythrocytes was inhibited by D-lactose (0.2 mM)> D-galactose (0.8 mM)> D-raffinose (2 .1 mM). At pH 7.5, chromatography on a Superose 12 HR 10/30 column sho wed that the lectin was primarily a dimer (56.0 kDa) composed of two i dentical subunits (31.6 kDa each). A small amount of a tetrameric form was also apparently present. The lectin is a glycoprotein (7.3% carbo hydrate), has a pi of 4.5, contains high levels of acidic (Asp and Glu , 64.2 and 51.6 residues/mol, respectively) and hydroxy amino acids (S er and Thr, 42.9 and 38.5 residues/mol, respectively) but relatively l ow amounts of sulfur amino acids (Cys and Met, 1.0 and 5.0 residues/mo l, respectively) and has an N-terminal sequence of Val-Glu-Thr-Ile/Leu -Pro-Phe-Ser. Its hemagglutinating activity was abolished by heating a t 70 degrees C for 10 min. The activation energy (Delta G') required f or denaturation measured by loss of hemagglutination activity was 24.8 7 kcal/mol. In rats, the purified lectin (100 mu g) induced neutrophil migration into the peritoneal cavity (3.7 +/- 0.6 x 10(6) neutrophils /ml) or into the air pouch (2.75 +/- 0.25 x 10(6) neutrophils/ml), 8 a nd 10 times greater than the negative control, respectively.