Preparation and characterization of human interleukin-5 expressed in recombinant Escherichia coli

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Abstract
The gene coding for human interleukin-5 was synthesized and expressed in Escherichia coli under control of a heat-inducible promoter. High-level expression, 10-15% of total cellular protein, was achieved in E. coli. The protein was produced in an insoluble state. A simple extraction, renaturation and purification scheme is described. The recombinant protein was found to be a homodimer, similar to the natural murine-derived protein. Despite the lack of glycosylation, high specific activities were obtained in three ''in vitro'' biological assays. Physical characterization of the protein showed it to be mostly .alpha.-helical, supporting the hypothesis that a conformational similarity exists among certain cytokines.