Purification and characterization of non-fusion recombinant human interleukin-18 expressed in E. coli

Objective To develop the purification method of rhIL 18 expressed in E coli Methods The harvested cells were disrupted using lysozyme and sonication The rhIL 18 inclusion bodies were extracted by centrifugation Washed inclusion bodies were solubilized in 8 mol/L urea The solubilized inclusion bodies were first purified by ion exchange chromatography under denaturing conditions After renaturation, gel filtration chromatography was used for further purification Samples were analyzed by SDS PAGE, HPLC, Western blotting and N terminal amino acid sequencing The biological activity of purified rhIL 18 was also measured Results It was found that rhIL 18 was expressed intracellularly in E coli as insoluble inclusion bodies The purity of rhIL 18 in extracted inclusion bodies was above 80% The final purified rhIL 18 was of high purity and exhibited the mass of molecule 19×10 3 by SDS PAGE The sequence of 15 amino acid residues form NH2 terminus of the purified rhIL 18 was consistent with the predicted sequence The purified rhIL 18 also induced IFN γ production of Con A stimulated human PBMC Conclusion The established method for purifying rhIL 18 is simple and effective and might be useful in the development of the large scaled purification process of rhIL 18