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 labeled with fluorescein isothiocyanate (FITC) and has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. FITC conjugates have been used in a variety of immunohistochemical and flow cytometry applications. Fluorescein conjugates display a high rate of photobleaching, signal is sensitive to pH changes, broad fluorescence emission spectrum, and fluorescence quenching on conjugation to biopolymers.