A new unusual galactose-specific lectin from the seeds of Indian lablab beans

Abstract

Seeds of the Indian lablab beans (Dolichos lablab var. typicus) contain a glucose/mannose-specific lectin that was affinity-purified and well characterized from our laboratory1. The seeds were also found to contain a protein that strongly agglutinates only rabbit erythrocytes. The agglutinating activity is inhibited only by galactose and its derivatives. However, this newly found lectin fails to bind on the sepharose-galactose columns, and hence was isolated by gel filtration on Biogel P-200. The lectin eluted from this column with a molecular size of 1,20,000 and was found to be homogeneous in native PAGE. In SDS-PAGE the lectin dissociated into two subunits with apparent molecular masses of 48 and 20 kDa, respectively. Alanine was the only detectable amino terminal amino acid. The lectin was found to be a glycoprotein with 3% neutral sugar and cross-reacts with an antibody to the well-characterized glucose/mannose specific seed lectin.