The nature of lectins from Dolichos lab lab.

The lectins from the seeds of Dolichas lablab var, lignosus field bean)and Dolichus
lablab var. typicus (lablab bean) have been isolated in a homogeneous form by affinity
chromatography on D-mannose linked Sepharose, Both the lectins are g1ycoproteins and have
a molecular weight of 60,000 and S20 value of 5.2 and seem to be made up of 4 similar
subunits (apparent molecular weight 15,000). Thecarbohydrate content ofthe lectins is mostly
fucose (2-5 mol per mol of protein), mannose (5-8 mol per mol of protein) and N·acetyl
glucosamine (1-2 mol per mol of protein). The amino acid composition of both the lectins was
similar and methionine and half cystine could not be detected, Both the lectins have similar
tryptic peptide map. Alanine and serine were the only Nand C-terminal amino acids for both
lectins. The lectins were found to contain low amounts of bound metals such as manganese,
magnesium and calcium. The near ultra-violet circular dichroism spectra of the lectins are
similar to that of Sainfoin. Circular dichroism data indicate thaI tyrosine and tryptophan
residues are involved in sugar binding.
The lectins are nonspecific for human blood groups and they agglutinate a variety of other
erythrocytes. Among a number of sugars, D-g1uoose and D-mannose inhibited the haemagglutinating
activity of the lectins. The lectins were antigenica1ly similar.