Isolation and characterization of a Forssman antigen-binding lectin from velvet bean (Mucuna derringiana) seeds.

A Forssman antigen (GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc beta 1-1Cer)-binding lectin has been purified from velvet bean (Mucuna derringiana) seeds by a combination of affinity chromatography and reversed phase HPLC. This lectin agglutinates both native and trypsin-treated sheep erythrocytes as well as trypsinized rabbit erythrocytes, but neither native rabbit nor human erythrocytes, irrespective of blood group type. SDS-PAGE and gel filtration chromatography reveal the lectin to be a homodimer consisting of two 54 kDa subunits linked by non-covalent bonds. The results obtained by quantitative precipitation, haemagglutination inhibition and TLC overlay assays indicate that the Mucuna lectin specifically recognizes Forssman antigen and Forssman disaccharide (GalNAc alpha 1-3GalNAc)-related structures.