Psophocarpus tetragonolobus lectin (PTL I, psophocarpin B1, a storage protein with chymotrypsin inhibitory activity), is isolated from winged bean seeds and purified by affinity chromatography. The seed contains two lectins in which PTL I is the basic of the two. PTL I is a dimeric glycoprotein with specificity to GalNAc, with eluting sugar GalNAc. This lectin agglutinates trypsinized rabbit and human erythrocytes (type A and B) but not trypsinized human type O erythrocytes. PTL I recognize blood group A-substance derived oligosaccharides such as trisaccharide GalNAcα1-3Galβ1-4Glc.
Psophocarpus tetragonolobus Lectin (PTL/PTA I) 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.