2 HEVEIN HOMOLOGS ISOLATED FROM THE SEED OF PHARBITIS-NIL L. EXHIBIT POTENT ANTIFUNGAL ACTIVITY

Two antifungal peptides (Pn-AMP1 and Pn-AMP2) have been purified to ho mogeneity from seeds of Pharbitis nil. The amino acid sequences of Pn- AMP1 (41 amino acid0 residues) and Pn-AMP2 (40 amino acid residues) we re identical except that Pn-AMP1 has an additional serine residue at t he carboxyl-terminus. The molecular masses of Pn-AMP1 and Pn-AMP2 were confirmed as 4299.7 and 4213.2Da, respectively, Both the Pn-AMPs were highly basic (pI 12.02) and had characteristics of cysteine/glycine r ich chitin-binding domain. Pn-AMPs exhibited potent antifungal activit y against both chitin-containing and non-chitin-containing fungi in th e cell wall. Concentrations required for 50% inhibition of fungal grow th were ranged from 3 to 26 mu g/ml for Pn-AMP1 and from 0.6 to 75 mu g/ml for Pn-AMP2. The Pn-AMPs penetrated very rapidly into fungal hyph ae and localized at septum and hyphal tips of fungi, which caused burs t of hyphal tips. Burst of hyphae resulted in disruption of the fungal membrane and leakage of the cytoplasmic materials. To our knowledge, Pn-AMPs are the first hevein-like proteins that show similar fungicida l effects as thionins do. (C) 1998 Elsevier Science B.V.