Cereal Chem 58:542 - 546.  |  VIEW ARTICLE
Disulfide Structures of Zein Proteins from Corn Endosperm.

J. W. Paulis. Copyright 1981 by the American Association of Cereal Chemists, Inc. 

Zein, the prolamine fraction of corn protein, consists of a series of disulfide-linked oligomers varying in molecular weight and intramolecular disulfide-bonded polypeptides, as demonstrated by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Whole native zein from normal corn was fractionated with 95% enthanol to obtain a soluble alpha-fraction and an insoluble beta-fraction. The unreduced alpha-fraction consisted of a series of oligomers; SDS-PAGE revealed a prominent band at a molecular weight of 24,000. The native alpha-component was heterogeneous by both PAGE at pH 3.5 and by isoelectric focusing between pH 6 and 9. The beta-component did not migrate into the gel during SDS- PAGE and showed only a streak following PAGE at pH 3.5 because it was too high in molecular weight. The alpha- and beta-fractions after reduction of disulfides exhibited both 22,000 and 24,000-mol wt subunits upon SDS-PAGE. Native zein from high-lysine corn (opaque-2) contained no 22,000-mol wt monomers. However, reduced opaque-2 zein contained 22,000-mol wt subunits but had a smaller proportion of 24,000-mol wt subunits than did normal zein. Fundamental compositional and functional differences in the 22,000 and 24,000-mol wt categories of zein polypeptide chains may result in differences in properties of normal and high-lysine zeins.