Submitted to: Proteome Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2014
Publication Date: 2/11/2014
Publication URL: http://dx.doi.org/10.1186/1477-5956-12-8
Citation: Vensel, W.H., Tanaka, C.K., Altenbach, S.B. 2014. Protein composition of wheat gluten polymer fractions determined by quantitative two-dimensional gel electrophoresis and tandem mass spectrometry. Proteome Science. DOI:10.1186/1477-5956-12-8.
Interpretive Summary: Wheat flour contains a complex mixture of proteins, some of which form large polymers that have been shown to be essential for producing good quality products. Despite their importance, it has been very difficult to study the protein composition of these polymers due to their large size and unusual solubility. This manuscript describes the separation of wheat flour proteins into fractions containing large and small gluten polymers and the detailed analysis of the protein components in each fraction. The study identifies proteins that are preferentially accumulated in fractions containing small gluten polymers. The data suggests that these proteins may be responsible for decreasing the quality of wheat flour by limiting the size of the gluten polymer.
Technical Abstract: Flour proteins from the US bread wheat Butte 86 were extracted in 0.5% SDS using a two-step procedure with and without sonication and further separated by size exclusion chromatography into monomeric and polymeric fractions. Proteins in each fraction were analyzed by quantitative two-dimensional gel electrophoresis (2-DE) and proteins in select spots were identified by tandem mass spectrometry (MS/MS). Overlapping 2-DE spots from different protein fractions often yielded different identifications, highlighting the complexity of the wheat flour proteome. Based on the MS/MS identifications, the proportions of individual gluten protein types in the insoluble polymer fraction were determined. Most high-molecular-weight and low-molecular-weight glutenin subunits partitioned into the polymer fractions, while most gliadins were found in the monomer fractions. The exceptions were alpha, gamma and omega gliadins containing odd numbers of cysteine residues. These proteins were detected in all fractions, but were most abundant in the SDS-soluble polymer fraction, supporting the hypothesis that these gliadins serve as chain terminators of the polymer chains. Several types of non-gluten proteins also were found in the polymer fractions, including serpins, triticins and globulins. All three types preferentially partitioned into the SDS-soluble polymer fraction. These data make it possible to formulate hypotheses about how protein composition influences polymer size and structure and provide a foundation for future experiments aimed at determining how environment affects gluten polymer distribution.