Expression and purification of human IL-2 protein from Escherichia coli

Abstract

Human interleukin 2 protein (IL-2) is an important cytokine found to be elevated in several types of cancer. A synthetic DNA sequence of the cDNA of mature IL-2 protein was cloned into the pRSET-B expression vector. The expressed IL-2 protein in Escherichia coli [BL21] was associated with the formation of insoluble inclusion bodies (IBs). The effect of different cultivation conditions (temperature, isopropyl-β-D-thiogalactoside concentration, and early harvest of cells) together with the incorporation of single or dual His-tag on the formation of IBs of the expressed protein was investigated. Yet, expression of soluble IL-2 was not achieved under any of the investigated conditions. A simple protocol for rapid and effective solubilization of these IBs was optimized. Using this protocol, together with subsequent purification using ion metal affinity chromatography, a purified His-IL2 protein was obtained in a yield of 5.1 mg/cell pellet of 1 L culture. In conclusion, the effect of different expression conditions on the solubility behavior of an expressed eukaryotic protein in E. coli was investigated using human IL-2 as a model protein. Moreover, the purified expressed protein could be used as a positive control in early diagnosis of tumors and in cancer research in Egypt.