High-Level Expression, Purification, and Renaturation of Recombinant Murine Interleukin-2 from Escherichia coli

A murine interleukin-2 (mIL-2)-encoding cDNA, isolated from a stimulated EL4 mRNA library, was used to construct several expression plasmids directing synthesis of the mature protein in Escherichia coli. The expression was under control of either the P Trp or the P L promoter. Using these systems, a high-level expression of between 10 and 35% of the total cellular protein was obtained. The mIL-2 protein, present as insoluble inclusion bodies, could be solubilized in a chaotropic mixture and was partially purified by preparative gel filtration under denaturing conditions. After renaturation, the protein was further purified to homogeneity by anion-exchange chromatography. Depending on the fermentation, induction, and renaturation conditions, the yield ranged between 0.35 and 1 mg of purified mIL-2/g wet cells. The specific biological activity was about 10 7 units/mg and the endotoxin content