Zeamatin, an antifungal protein from maize with membrane-permeabilizing activity

A 22 kDa antifungal protein (zeamatin) was purified from Zea mays seeds. It was identified and assayed by its unusual property of acting synergistically with nikkomycin to inhibit growth of Candida albicans. Alone, it inhibited growth in suspension culture of C. albicans, Neurospora crassa and Trichoderma reesei. Zeamatin contained no detectable chitinase, 1,3-β-glucanase or ribosome-inactivating protein activity, enzymes present in a variety of plants that have been shown to have antifungal properties. At low concentrations zeamatin caused the rapid release of cytoplasmic material from C. albicans and N. crassa. This was confirmed microscopically by observing zeamatin-induced hyphal rupture of these fungi. These results suggest that zeamatin permeabilizes the fungal plasma membrane. We believe zeamatin to be a representative of a previously unrecognized class of plant antifungal proteins.