Cereal Chem. 70:581-585   |  VIEW ARTICLE

D-Glutenin Subunits: N-Terminal Sequences and Evidence for the Presence of Cysteine.

S. Masci, D. Lafiandra, E. Porceddu, E. J.-L. Lew, H. P. Tao, and D. D. Kasarda. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

The two-chromosome, 1D-coded D subunits of low molecular weight glutenins from Chinese Spring wheat were purified by using preparative isoelectric focusing and reversed-phase high-performance liquid chromatography. Their N-terminal sequences corresponded to those of the two-chromosome, 1D-coded omega-gliadins, which they also resemble in molecular weight and isoelectric point. In order to show the presence of cysteine in D subunits, which should account for their presence in glutenin, the reduced subunits were reacted with a fluorogenic reagent specific for sulfhydryl groups in a mixture with the 1D-controlled omega-gliadins that were assumed to have no cysteine residues. When the mixture was separated in a reversed-phase high-performance liquid chromatography system equipped with UV absorbance and fluorescence detectors in series, all components were detected by UV absorbance, but only the peaks corresponding to the D subunits showed fluorescence. This confirmed the presence of at least one cysteine in the D glutenin subunits. If only one cysteine residue is present, which seems likely, it is possible that D subunits would negatively influence quality characteristics because they would be able to form only intermolecular disulfide bonds, thereby acting as terminators of the growing glutenin polymers.