What is "thionin"

n. 1 (alternative form of thionine English) 2 (context protein English) Any of a class of cytotoxic polypeptides found in some plants

Thionins (without an e) are a family of small proteins found solely in higher plants. Typically, a thionin consists of 45–48 amino acid residues. 6–8 of these are cysteine forming 3–4 disulfide bonds. Alpha- and beta- thionins are related to each other. The gamma thionins have a superficially similar structure but are an unrelated class of protein, now called plant defensins.