Quality-related Epitopes of High Mr Subunits of Wheat Glutenin

Abstract

Abstract Three hundred and eighty four immobilised overlapping nonapeptides, corresponding to the full amino acid sequences of three high Mr subunits of glutenin from bread wheat (Triticum aestivum) grain, were used to determine the linear epitopes recognised by four monoclonal antibodies. These antibodies were selected on the basis of significant and positive correlations between their binding to wheat flour extracts in a two-site ('sandwich') enzyme immunoassay and rheological measures of dough strength, an important aspect of bread wheat quality. The antibodies did not bind to a single, specific sequence but bound a series of related peptides in each high Mr glutenin subunit examined. The sequences recognised were not identical for the four antibodies, but in each case were in the central repeating domain of the high Mr glutenin subunits, and usually comprised regions that overlapped the degenerate repeat nonamer and hexamer sequences. High Mr glutenin subunits that have been associated with greater dough strength, such as the D-genome allelic products 1Dx5 and 1Dy10, displayed an increased number of the epitope sequences. The location of the epitopes in sequences of overlapping β-turns in the repetitive region supports the hypothesis that dough elasticity arises partly from β-turn-forming secondary structure in the repeat regions of the Mr glutenin subunits. Additional β-turn within high Mr subunits may extend their structure to allow increased interaction between the glutenin subunits and with the other proteins of the gluten complex, thus improving dough strength.