Over-expression and refolding of β-subunit from the chloroplast ATP synthase

AbstractWe established a bacterial system for high-level over-expression of the spinach chloroplast atpB gene which encodes the ATP Synthase β subunit. Upon induction, atpB was expressed as at least 50% to 70% of total cell protein. Although the over-expressed β polypeptide formed insoluble inclusion bodies, more than fifty percent of it was restored to a functional form by solubilizing the inclusion bodies with 4 M urea and slowly removing the urea by stepwise dialysis. The resulting β subunit exhibited specific and selective nucleotide binding properties identical to those of the native β subunit