Purification of recombinant human tumor necrosis factor precursor from Escherichia coli

To study its biological functions, tumor necrosis factor precursor (proTNF) with a molecular size of 26-KDa was obtained as a recombinant protein from Escherichia coli. The recombinant proTNF was successfully accumulated in the insoluble form, corresponding to about 10-15% of total E. coli proteins. Solubilization, gel filtration and anion exchange chromatography were performed under denatured conditions followed by dialysis in phosphate-buffered saline. These processes removed most of the contaminating bacterial proteins, yielding proTNF with a purity of about 70-80%. This recombinant proTNF is expected to be useful for functional studies on activated macrophages with membrane integrated proTNF.