Purification and characterization of the gonad lectin of Aplysia depilans

Extracts of gonads and fertilized eggs of Aplysia depilans contain a D-galacturonic and D-galactose-binding lectin. This lectin reacts strongly with rabbit and human erythrocytes independent of ABO blood groups, weakly with dog, mouse, rat, and chick erythrocytes and not at all or very weakly with sheep erythrocytes. Purification of the gonad lectin was easily achieved, with a high yield, by heating to 70 degrees C, precipitation with ammonium sulfate and affinity chromatography on Sepharose 4B. The purified lectin was found to be a glucoprotein of molecular mass around 55-60 kDa; it stimulates mitogenesis of human peripheral lymphocytes.