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Characterization of the 1B-Type ω-Gliadins from Triticum aestivum Cultivar Butte

¹Corresponding author. Phone: 510-559-5702. Fax: 510-559-5818. E-mail: fmd@pw.usda.gov ²USDA Agricultural Research Service, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

ω-Gliadins were purified from wheat (Triticum aestivum L. ‘Butte’) flour and characterized. Although reversed-phase HPLC (RP-HPLC) separated the 1B-encoded ω-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 ω-gliadin internal repeat was QQQXP, where X was F, I, or L in descending order of occurrence. The 1D-encoded ω-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 ω-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.