Isolation and Characterization of a Lectin from Japanese Mottled Beans

A 64-kDa dimeric lectin was purified from Phaseolus vulgaris cv. Japanese mottled beans. The purification protocol involved ion exchange chromatography with Q-Sepharose and SP-Sepharose and size exclusion chromatography on Superdex 75. The lectin was adsorbed on both Q-Sepharose and SP-Sepharose columns. Finally, the lectin gave a sharp absorbance peak which corresponded to 64 kDa based on results of size exclusion chromatography. Sodium dodecyl sulphate- polyacrylamide gel electrophoresis displayed a single band at around 32 kDa, indicating that the protein was dimeric. The hemagglutination inhibition assay indicated that the lectin showed specificity toward galactose. The lectin preserved hemagglutinating activity below 70 °C and at a pH range 3 – 12. The lectin was able to inhibit proliferation of MCF-7 cells and Hep G2 cells and possessed antifungal activity toward Mycosphaeralla arachidicola with an IC 50 value of 3.9 µM. The activity of HIV-1 reverse transcriptase was reduced by 61.9 % in the presence of the lectin at 6.25 µM concentration.