Griffonia simplicifolia lectin (GSL I) is affinity purified from a woody climbing shrub native to Africa. GSL I is composed of two types of subunits A and B that combine to form tetrameric structures, resulting in five isolectins. This lectin has affinity for terminal ?-D-galactosyl residues and terminal N-acetyl-?-D-galactosaminyl residues. The A-rich lectin preferentially agglutinates blood group A erythrocytes and thus appears to be specific for ?-N-acetylgalactosamine residues, while the B-rich lectin preferentially agglutinates blood group B cells and is specific for ?-galactose residues. This lectin shows specificity for blood group B greater than blood group A1.
GSL I has been reported to bind several glycoproteins including laminin. Since some ?-D-galactosyl residues are expressed in endothelial cells of mouse tissues, GSL I can present a highly specific surface of glycosylation pattern in these cells.