Cys/Gly-rich proteins with a putative single chitin-binding domain from oat (Avena sativa) seeds

Through a reliable and repeatable procedure based on solid-phase extraction techniques, a protein fraction (P fraction) rich in Cys/Gly residues was extracted and captured from oat (Avena sativa L.) seeds. Quantitative amino acid analysis and MS of the P fraction indicated that it contains a series of heterogeneous Cys/Gly-rich proteins with molecular masses of 3.6-4.0 kDa. Preliminary results from bioassays showed that these proteins possess weak to moderate antifungal properties to some fungal strains. From this fraction, a new polypeptide, designated avesin A, was purified and sequenced by Edman degradation. Avesin A consists of 37 amino-acid residues, with 10 glycine residues and eight cysteine residues forming disulfide bridges, and contains a single chitin-binding domain, which indicates that avesin A is a new member of the putative chitin-binding proteins. Avesin A is the first identified hevein-like small protein from cereal grains.