Tandem repeats in the N-terminal sequence of a proline-rich protein from corn endosperm

Zeins, the prolamines of corn (Zea mays), are the most abundant storage protein fraction in corn endosperm. Like prolamines of other cereals, zeins are readily soluble in 60–70% alcohol solutions but are insoluble in aqueous buffer systems. The other major storage protein fraction in corn endosperm is glutelin, which is extractable with either dilute alkali or detergent. We have now extracted from corn endosperm a prolinerich, zein-like protein fraction which we have purified by chromatography on phosphocellulose. Study of the N-terminal sequences of three chromatographic fractions for homologies shows that they are essentially identical. These N-terminal sequences include a hexapeptide Pro-Pro-Pro-Val-His-Leu, which is repeated in tandem at least six times, and probably eight times or more.