Modification of maize-seed-protein quality.

The storage proteins of maize are a group of alcohol-soluble polypeptides called zeins. These proteins are synthesized in the developing endosperm, where they form protein bodies within the rough endoplasmic reticulum. Because they account for more than half of the total seed protein, zeins are the primary determinants of the amino acid composition of the seed. All of the zeins are devoid of lysine an essential amino acid for monogastric animals. We have modified the genes encoding zeins so that they encode proteins that contain lysine and tryptophan. Analysis of the synthesis and processing of these modified zein proteins indicates that the addition of lysine and tryptophan does not interfere with their association into protein bodies.