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Characterization of the 1B-type omega-gliadins from Triticum aestivum cultivar butte

DuPont, F.M., Vensel, W.H., Chan, R., Kasarda, D.D.
Cereal chemistry 2000 v.77 no.5 pp. 607-614
wheat, Triticum aestivum, gliadin, food composition, protein composition
omega-Gliadins were purified from wheat (Triticum aestivum L. 'Butte') flour and characterized. Although reversed-phase HPLC (RP-HPLC) separated the 1B-encoded omega-gliadins into two fractions, 1B1 and 1B2, these fractions had nearly identical amino acid compositions, three similar protein bands in SDS-PAGE, 10 similar spots in two-dimensional PAGE, and two similar N-terminal amino acid sequences. The main components had a range in mass of 48,900-51,500 when estimated by mass spectrometry, significantly less than the mass estimated by SDS-PAGE. The 1B fractions were digested with thermolysin, the peptides were separated by RP-HPLC, the peptide mass was determined, and nine peptides from each fraction were sequenced with nearly identical results for the 1B1 and 1B2 digests. A possible consensus sequence of the 1B-encoded omega-gliadin internal repeat was QQQXP, where X was F, I, or L in descending order of occurrence. The 1D-encoded omega-gliadins were purified by RP-HPLC as a single fraction that had one band in SDS-PAGE, two spots in two-dimensional PAGE, two components with mass of 41,923 and 42,770 detected by mass spectrometry, and two N-terminal sequences. Circular dichroism (CD) spectra for the 1B and 1D omega-gliadins were similar and were suggestive of mainly flexible random structure with a significant amount of the left-handed polyproline II helical conformation in the 1D components.