Comprehensive examination of protein distribution profile in wheat grain

A wheat grain was divided into three portions, endosperm, germ and bran, and the protein profile of each was examined comparatively after sequential extraction with isopropyl alcohol, sodium chloride, lactic acid and KOH solutions. Recovery of the protein in the extracts was 93-96%. The relative protein concentrations of the four soluble fractions of endosperm were very similar to those of bran, but germ showed a distinct distribution of the soluble proteins. Soluble protein fractions of endosperm, germ and bran, particularly their NaC1 soluble fractions, exhibited distinct individuality upon examination by polyacrylamide gel electrophoresis and gel filtration. Indeed, it was suggested that the gel electrophoretic profile could serve as a criterion for the quality evaluation of wheat flour. On the other hand, the KOH soluble proteins of endosperm, germ and bran, which gave indiscrete electrophoretic patterns, existed predominantly in highly aggregated forms which disintegrated upon exposure to 1% SDS or by reduction with 2-mercaptoethanol.