Zeins are seed storage proteins. They are unusually rich in glutamine, proline, alanine, and leucine residues and their sequences show a series of tandem repeats [1].

1: Studies of the zein-like alpha-prolamins based on an analysis of amino acid sequences: implications for their evolution and three-dimensional structure. Garratt R, Oliva G, Caracelli I, Leite A, Arruda P; Proteins 1993;15:88-99. PMID:8451243