Bauhinia purpurea agglutinin or lectin (BPA/BPL) is a tetrameric lectin with a molecular weight of 195,000. Binding appears to be highest for glycoconjugates containing galactosyl (β-1,3)N-acetylgalactosamine structures but oligosaccharides with a terminal α-linked N-acetylgalactosamine can also bind. BPA is lactose-specific and elutes with the sugar lactose. It has specificity for blood groups A, B, O (-SA). Treatment of erythrocytes with neuraminidase or trypsin will increase the agglutination reaction, indicating that the receptor is masked by terminal carbohydrates.
Although binding specificity is similar to that of peanut agglutinin, tissue staining patterns of these two lectins are distinct. Makela's group 2 sugars, particularly N-acetyl-D-galactosamine, are potent inhibitors. The native protein appears to be stable in detergent solution.
Bauhinia purpurea Lectin (BPL/BPA) is conjugated to ferritin, that has a molecular weight of 474,000 g/mol (all 24 subunits combined). Ferritin-conjugated lectins can be used to visualize localization of specific saccharide moieties and examine the distribution of plasma membrane glycoproteins. These conjugates can be viewed via electron microscopy.