Human recombinant interleukin-1 beta isolated from Escherichia coli by simple osmotic shock

A synthetic gene coding for the C-terminal 153 amino acids of the human interleukin-1 beta (IL-1 beta) was used to produce large quantities of recombinant IL-1 beta in Escherichia coli. The expression of the synthetic gene was under the control of an inducible promoter. The recombinant protein was released from the cells by an osmotic shock. This procedure did not lyse the cells. The IL-1 beta that represented 90% of the total extracted protein was purified to homogeneity by a single chromatographic step. Sequence analysis revealed a heterogeneous N-terminal sequence resulting from the cleavage of the N-terminal methionine in 50% of the molecules and of both the N-terminal methionine and alanine in the other 50%. This recombinant IL-1 beta had a specific activity of 1.3 x 10(8) international units per mg.