Characterization of a Low-Molecular-Weight Glutenin Subunit Gene from Bread Wheat and the Corresponding Protein That Represents a Major Subunit of the Glutenin Polymer

TLDR

High‑ and low‑molecular‑weight glutenin subunits are key determinants of wheat flour viscoelasticity, yet no clear link has been established between their DNA sequences and the proteins present in the endosperm. A computer‑generated molecular model of the 42K subunit was built from its deduced amino‑acid sequence and literature‑based disulfide‑linkage assignments. The 42K LMW‑GS was isolated, its gene sequenced, and amino‑acid data confirmed a protein–gene correspondence; the subunit lacks a cysteine at position 5, replaced by one in the repeat domain, leaving the total cysteine count unchanged.

Abstract

Abstract Both high- and low-molecular-weight glutenin subunits (LMW-GS) play the major role in determining the viscoelastic properties of wheat (Triticum aestivum L.) flour. To date there has been no clear correspondence between the amino acid sequences of LMW-GS derived from DNA sequencing and those of actual LMW-GS present in the endosperm. We have characterized a particular LMW-GS from hexaploid bread wheat, a major component of the glutenin polymer, which we call the 42K LMW-GS, and have isolated and sequenced the putative corresponding gene. Extensive amino acid sequences obtained directly for this 42K LMW-GS indicate correspondence between this protein and the putative corresponding gene. This subunit did not show a cysteine (Cys) at position 5, in contrast to what has frequently been reported for nucleotide-based sequences of LMW-GS. This Cys has been replaced by one occurring in the repeated-sequence domain, leaving the total number of Cys residues in the molecule the same as in various other LMW-GS. On the basis of the deduced amino acid sequence and literature-based assignment of disulfide linkages, a computer-generated molecular model of the 42K subunit was constructed.