Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2010
Publication Date: 9/1/2010
Citation: Altenbach, S.B., Vensel, W.H., Dupont, F.M. 2010. Integration of transcriptomic and proteomic data from a single wheat cultivar provides new tools for understanding the roles of individual alpha gliadin proteins in flour quality and celiac disease. Journal of Cereal Science. 52:143-151. Interpretive Summary: The alpha gliadins are a complex group of proteins that together with other gluten proteins determine the functional properties of wheat flour. Some of these proteins are also a major factor in celiac disease, a widespread autoimmune disease caused by ingestion of wheat. The proteins have unusual amino acid compositions and contain large regions of repetitive sequences. While most alpha gliadins are present in the flour as single proteins, some contain minor sequence variations that enable them to be linked with other gluten proteins into large polymers that are critical for flour quality. The ability to differentiate among the alpha gliadins is important for studies of flour quality because proteins with similar sequences can have different effects on functional properties and on the promotion of celiac disease. Mass spectrometry is often used to identify proteins. However, it is challenging to use mass spectrometry to identify the wheat alpha gliadins because of the complexity of the proteins and the lack of complete sequence information in databases that are used to evaluate mass spectrometry data. To overcome these problems, a detailed analysis of alpha gliadin genes expressed in a US wheat cultivar was performed. The inclusion of these cultivar-specific sequences in databases used to analyze mass spectrometry data made it possible to distinguish individual alpha gliadins that play different roles in flour quality and human health.
Technical Abstract: One-hundred-thirty-six expressed sequence tags (ESTs) encoding alpha gliadins from Triticum aestivum cv Butte 86 were identified in public databases and assembled into 19 contigs. Consensus sequences for 12 of the contigs encoded complete alpha gliadin proteins, but only two were identical to proteins reported previously in the NCBI non-redundant database. Comparison of the encoded proteins revealed one alpha gliadin that contains an additional cysteine residue that might allow incorporation of the protein into glutenin polymers. Differences in epitopes related to celiac disease were observed among the proteins and two new types of alpha gliadins ending in GFFGTN and GIMSTN were identified. Specialized databases that included the sequences of Butte 86 alpha gliadins were constructed for identification of flour proteins by tandem mass spectrometry (MS/MS). In a pilot experiment, proteins corresponding to 12 of the alpha gliadins encoded by Butte 86 contigs were distinguished by MS/MS. Unique peptide tags that differentiate each of these proteins are reported.