Two novel antifungal peptides distinct with a five-disulfide motif from the bark of Eucommia ulmoides Oliv

Abstract

Two antifungal peptides, named EAFP1 and EAFP2, have been purified from the bark of Eucommia ulmoides Oliv. Each of the sequences consists of 41 residues with a N-terminal blockage by pyroglutamic acid determined by automated Edman degradation in combination with the tandem mass spectroscopy and the C-terminal ladder sequencing analysis. The primary structurs all contain 10 cysteines, which are cross-linked to form five disulfide bridges with a pairing pattern (C1–C5, C2–C9, C3–C6, C4–C7, C8–C10). This is the first finding of a plant antifungal peptide with a five-disulfide motif. EAFP1 and EAFP2 show characteristics of hevein domain and exhibit chitin-binding properties similar to the previously identified hevein-like peptides. They exhibit relatively broad spectra of antifungal activities against eight pathogenic fungi from cotton, wheat, potato, tomato and tobacco. The inhibition activity of EAFP1 and EAFP2 can be effective on both chitin-containing and chitin-free fungi. The values of IC 50 range from 35 to 155 μg/ml for EAFP1 and 18 to 109 μg/ml for EAFP2. Their antifungal effects are strongly antagonized by calcium ions.