Production of recombinant rat interleukin-6 in Escherichia coli using a novel highly efficient expression vector pGEX-3T

Interleukin-6 (IL-6) is one of the most important mediators of the acute phase reaction in liver. For the production of recombinant rat IL-6 in Escherichia coli, a previously isolated cDNA coding for the rat IL-6 was cloned into the modified novel expression vector pGEX-3T. The IL-6 cDNA was highly expressed as a fusion protein with the glutathione S-transferase (GST) at its C-terminus and rat IL-6 at its N-terminus. The GST-IL-6 fusion protein was controlled by a tac-promoter and could be induced very efficiently by isopropyl-beta-D-thiogalactopyranoside. The synthesized GST-IL-6 fusion protein was insoluble and precipitated intracellularly in E. coli. Using an advanced technique, the insoluble protein was solubilized and purified to homogeneity by affinity chromatography using immobilized glutathione in a one-step procedure.