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 tetramethylrhodamine isothiocyanate (TRITC) and has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. TRITC is a bright orange or red-fluorescent dye with excitation ideally suited to the 532-nm laser line. TRITC labeled PTL/PTA I can be used for cellular imaging applications.