Heterologous expression of a wheat high molecular weight glutenin gene in Escherichia coli.

An engineered DNA fragment containing a DNA sequence encoding a wheat high molecular weight glutenin subunit was cloned into a bacterial expression vector that is based on bacteriophage T7 RNA polymerase. The resulting plasmid directed the synthesis of large amounts of the mature form of the wheat high molecular weight glutenin subunit in Escherichia coli. This protein comigrated in SDS/PAGE with a native high molecular weight glutenin subunit extracted from wheat endosperm and cross-reacted with antibodies raised against purified wheat high molecular weight glutenins. The wheat subunit synthesized in E. coli also exhibited pI and solubility characteristics identical to those of native wheat subunits. Moreover, the wheat glutenin subunit produced in E. coli cells self-assembled into oligomers linked by intermolecular disulfide bonds, a process that plays an important role in the assembly of native glutenins during gluten formation. The large amounts of a purified wheat subunit obtained from E. coli will enable investigators to analyze the three-dimensional structure of that protein and to identify protein sequences that affect the bread-making quality of wheat dough.