High-Level Expression of a Wheat LMW Glutenin Subunit Using a Baculovirus System

A wheat gene encoding a low molecular weight (LMW) subunit of glutenin was expressed in cultured insect cells using a baculovirus vector. The LMW subunit accounted for 25–30% of the extracted protein; 30–50 mg was readily purified from 1 L of culture by solubility in 50% (v/v) aqueous propanl-ol followed by salt precipitation. The plant signal sequence was apparently cleaved, and the protein accumulated as disulfide-bonded polymers in dense deposits within the lumen of the rough endoplasmic reticulum. The expressed protein was less soluble than LMW subunits prepared from wheat, and over 90% was irreversibly absorbed to a column of CM-cellulose. However, the protein eluted from the column did show more typical solubility properties and could be refolded to give a mixture of monomers and disulfide-stabilized polymers using slow dialysis or rapid dilution methods. Circular dichroism spectroscopy of the refolded protein showed secondary structure contents similar to LMW subunits purified from wheat.