141 Characterization of 1B omega gliadins from wheat.

F. M. DUPONT, W. H. Vensel, R. Chan, and D. D. Kasarda. USDA, Agricultural Research Service, Western Regional Research Center, Albany, CA 94710.

We report the first detailed characterization of the 1B-coded omega gliadins. Omega gliadins were extracted from wheat (Triticum aestivum L. cv. Butte) flour, purified by RP-HPLC and characterized with respect to peptide sequence, amino acid composition, molecular weight and peptide pattern of thermolysin digests. Two 1B-coded omega gliadin fractions and one 1D-coded omega gliadin fraction were collected by RP-HPCL and characterized by SDS-PAGE. The identities of the fractions were confirmed by comparing the N-terminal amino acid sequences with published sequences. Although the two 1B fractions differed in retention time, and thus in hydrophobicity, they had nearly identical amino acid compositions and nearly identical patterns in SDS-PAGE, each having three bands with apparent mass of 60, 61 and 64 kDa. The 1D fraction had a single band in SDS-PAGE with apparent mass of 57 kDa. The masses of the components were lower, as determined by MALDI. The 1B fractions were digested with thermolysin, the peptides separated by RP-HPLC, and mass determined by MALDI, with nearly identical patterns for the peptides from the two fractions. Several thermolysin peptides were sequenced, giving the first information on the internal sequence of the 1B-coded omega gliadins. A consensus repeat sequence found in some peptides was PQQQ- or PQQQQ- followed by F, I, L or Y. Also, the CD spectra for the 1B and 1D omega gliadins were compared.