An antifungal defensin from Phaseolus vulgaris cv. ‘Cloud Bean’

Wu, Xiangli; Sun, Jian; Zhang, Guoqing; Wang, Hexiang; Ng, Tzi Bun

An antifungal peptide with a defensin-like sequence and exhibiting a molecular mass of 7.3 kDa was purified from dried seeds of Phaseolus vulgaris ‘Cloud Bean’. The isolation procedure entailed anion exchange chromatography on DEAE-cellulose, affinity chromatography an Affi-gel blue gel, cation exchange chromatography on SP-Sepharose, and gel filtration by fast protein liquid chromatography on Superdex 75. Although the antifungal peptide was unadsorbed on DEAE-cellulose, it was adsorbed on both Affi-gel blue gel and SP-Sepharose. The antifungal peptide exerted antifungal activity against Mycosphaerella arachidicola with an IC(50) value of 1.8 μM. It was also active against Fusarium oxysporum with an IC(50) value of 2.2 μM. It had no inhibitory effect on HIV-1 reverse transcriptase when tested up to 100 μM. Proliferation of L1210 mouse leukemia cells and MBL2 lymphoma cells was inhibited by the antifungal peptide with an IC(50) of 10 μM and 40 μM, respectively.