Purification and refolding of Escherichia coli‐expressed recombinant human interleukin‐2

The expression of rhIL‐2 (recombinant human interleukin‐2) in bacteria results in the formation of insoluble inclusion‐body aggregates. These aggregates were first solubilized under denaturing conditions (sodium phosphate buffer solution containing 8 M urea and 10 mM 2‐mercaptoethanol) and then purified using IMAC (immobilized metal‐ion‐affinity chromatography). IMAC was used to capture rhIL‐2. The protein was gradually refolded on the column by a gradient elution (8 M to 0 M urea) in the presence of 10% (v/v) glycerol. Glycerol was used to prevent protein aggregation during the refolding step. Using this method, rhIL‐2 was collected at 97% purity and its activity was measured by the lymphocyte transformation test. The measured activity was identical with commercial human interleukin‐2.