Purification and characterization of human interleukin-1alpha produced in Escherichia coli

Abstract

The production of human interleukin-1α (IL-1α) in Escherichia coli is described together with a method for its purification. The isolated protein was shown to be pure and physically homogeneous. The in vitro biological activity of IL-1α was tested with the mononuclear-cell factor and the lymphocyte-activating factor assays. The specific activity determined with both assays was about 3 × 10⁷ units mg⁻¹ and is similar to that observed with recombinant human IL-1β. The purified protein was resolved by chromatofocusing into two species of isoelectric points 5.45 and 5.20 (75% and 25%, respectively, of the total protein). Both species had similar chemical properties and biological activities to the unfractionated protein. The charge difference between the species was attributed to the deamidation of a single Asn or Gln residue.