Psophocarpus tetragonolobus lectin (PTL II, psophocarpin B1, a storage protein with chymotrypsin inhibitory activity), is isolated from winged bean seeds and purified by fractionation. The seed contains two lectins in which PTL II is the acidic of the two. This lectin agglutinates trypsinized and desialized erythrocytes of all three blood group types (A, B, and O). Nonpolar interactions play an important role in stabilization of the lectin-sugar complex. Projection of α1,3 linked Gal/GalNAc leads to steric hindrance and prevents the binding of blood group A and B reactive sugars.The unique specificity of PTL II makes it to be useful in isolation and characterization of terminally monofucosylated H-reactive oligosaccharides from those that are difucosylated or internally fucosylated.
Psophocarpus tetragonolobus Lectin (PTL/PTA II) 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.