Influence of salts and aggregation of gluten proteins on reduction and extraction of high molecular weight glutenin subunits of wheat

High-molecular weight glutenin subunits (HMW-GS) of wheat were extracted by various combinations of reducing agents, salt solutions, and solvents. Preferential extraction of 1D-encoded HMW-GS occurred when flours were extracted with Tris-HCl SDS buffer at pH 6.8 containing 6% mercaptoethanesulfonic acid sodium salt (MESNA) and analyzed by SDS-PAGE. Similar effects were also found when dithiothreitol or beta-mercaptoethanol were used in conjunction with nonchaotropic salts. If flours were first extracted with 50% 1-propanol, the extraction procedure yielded all HMW-GS, even in the presence of MESNA or high levels of salts. Addition of alcohols or chaotropes to the Tris buffer solutions containing MESNA or of solutions containing salt also extracted all HMW-GS. The HMW-GS reported most important in baking quality were found preferentially extracted by nonchaotropic salts and reducing agents. This is related to gluten aggregation and the gliadin-glutenin interaction and structure.