Purification of human erythrocytes specific lectins from rice bean, Phaseolus calcaratus syn. Vigna umbellata, by high-performance liquid chromatography.

Two lectins, an N-acetylgalactosamine-binding lectin, lectin-I, which reacts specifically with human erythrocytes of blood group A, and a galactose-binding lectin, lectin-II, which is specific for human blood group B erythrocytes, have been isolated and purified from rice bean, Phaseolus calcaratus syn. Vigna umbellata, by a salt solubility pH-dependent method, chromatofocusing and high-performance liquid chromatography. The homogeneity of the lectins was determined by liquid chromatography and polyacrylamide gel electrophoresis. The purified lectin-I of molecular mass 80,000 is possibly composed of two subunits of molecular mass ca. 18,000 and 22,000, respectively, whereas lectin-II of molecular mass 100,000 appears to be composed of a monomeric protein of molecular mass 25,000. One endogenous lectin-binding protein was also isolated and purified by liquid chromatography. The endogenous lectin-binding protein of molecular mass 40,000 affects the activity of the A-group specific lectin more than that of the B-group specific lectin. The endogenous lectin-binding protein appears to be composed of a monomeric protein of molecular mass 20,000.