Two-dimensional separation of prolamins of normal and high lysine barley (Hordeum vulgare L.)

The polypeptide components of the reduced prolamin fraction (hordein) of barley seed proteins have been separated, before and after alkylation, by polyacrylamide gel electrophoresis using buffers containing urea and/or sodium dodecylsulphate (SDS). Alkylation of the protein with 4-vinylpyridine or acrylonitrile results in a considerable sharpening of the protein bands and some minor changes in the band pattern. The procedure has been used to compare the hordeins of the normal commercial varieties, Julia and Bomi, to those of a high lysine mutant of Bomi (Rise, 1508). Whereas the alkylated hordein fractions of Bomi and Julia contain SDS bands of apparent molecular weights 13 000, 16 000, 20 000, 30 000, 43 000, 51 000, 67 000, and 86 000, the mutant hordein fractions contain predominantly the low molecular weight (13 000, 16 000, and 20 000) and mol. wt. 51 000 bands. Further resolution of the fractions was obtained by two-dimensional electrophoresis using 6 M urea in glycine/acetate buffer at pH 4·6 as the first dimension and SDS in tris/borate buffer at pH 8·9 as the second. Separation of the Rise 1508 hordein in this system demonstrated that the mol. wt. 51 000 band contains several closely similar components.