A model for the molecular structure of the glutenins from wheat flour

Protein fractions, which were termed glutenins I, IIa, IIb, IIIa and IIIb were isolated from flour of the Dutch wheat cultivar, Sicco, by extraction with sodium dodecyl sulphate (SDS) solution and fractionation by precipitation/redissolution techniques and by gel filtration chromatography. The fractions were subsequently characterised by polyacrylamide gel electrophoresis in the presence of SDS (SDS-PAGE). SDS-insoluble glutenin I is a polymer having an apparent molecular weight of 2 × 10 7 or more; the data indicated that it is formed from SDS-soluble glutenins IIa and IIb molecules that are linked through their constituent high molecular weight A subunits. The SDS-soluble and 70% ethanol-insoluble glutenins IIa and IIb have estimated average molecular weights of 8 × 10 5 and several million respectively. On the basis of the data obtained a model of glutenin structure is proposed, in which glutenin IIa is composed of three high molecular weight glutenin A subunits and four glutenin IIIa molecules: glutenin IIb is a linear polymer of glutenin IIa molecules. The SDS-soluble and 70% ethanol-soluble glutenins IIIa and IIIb have estimated average molecular weights of 1.2 × 10 5 , and 4.8 × 10 5 , respectively. Glutenin IIIa molecules are composed of low molecular weight glutenin B and C subunits. Glutenin IIIb molecules are formed from four glutenin IIIa molecules linked through disulphide bonds. In this hypothetical model for the structure of glutenin I and II, the high molecular weight glutenin A subunits are linked together via head-to-tail interchain disulphide bonds to form a linear chain. The low molecular weight glutenin B and C subunits form a cluster (glutenin III), which is linked via disulphide bonds to the A subunits of the linear chain that are designated subunits 10 or 11. © 1985, Academic Press Inc. (London) Limited. All rights reserved.