Studies on lectins. XLVII. Some properties of D-galactose binding lectins isolated from the seeds of Butea frondosa, Erythrina indica and Momordica charantia.

The lectins from the seeds of Butea frondosa, Erythrina indica and Momordica charantia were isolated by affinity chromatography on O-alpha-D-galactosyl polyacrylamide gels. The Butea frondosa lectin has sedimentation coefficient S20,W = 6.7 S, its molecular weight is 141 000 and it consists of noncovalently associated subunits of molecular weights 36 000 and 65 000. The lectin contains two 1/2-cystine and 3--4 methionine residues per molecule, 4.3% neutral sugar and 0.5% glucosamine. Threonine is the single N-terminal amino acid residue. The lectin from Erythrina indica seeds has a sedimentation coefficient S20,W = 4.0 S, its molecular weight is 66 200 and it consists of two kinds of subunit (molecular weights 30 000 and 34 000, respectively), which are noncovalently associated. The lectin is devoid of cystein, has a neutral sugar content 5.6% and glucosamine content 0.46%. It contains probably one Mn atom per subunit. The N-terminal amino acid sequence is Val-Glu-Val-Leu-(Phe)-Phe-(Ala)-Phe-. The lectin from Momordica charantia seeds has a sedimentation coefficient S20,W = 6.5 S, its molecular weight is 129 000. It interacts weakly with Sephadex G-200. The lectin consists of subunits of molecular weights 29 000, 32 000 and 36 000, respectively, held together by cystine bridges. Its content of cystine and methionine residues is relatively high, 4.1% neutral sugar and 0.5% glucosamine form the carbohydrate moiety. Two N-terminal amino acids (asparagine and valine) are present.