Effects of cytoplasmic recombinant protein expression (hll-2&mll-4) on hydrogen peroxide concentration and catalase activity in Escherichia coli

Abstract

The expression of a foreign protein(s) in a recombinant host cell or organism often changes the biochemistry and physiology of the host and lower the amount of the target foreign protein. Identification of preventive factors helps to resolve their inhibitory effects and improve the product yield by increasing cell growth and recombinant proteins production from molecular cloning to bioprocess procedures.The Reactive oxygen species (ROS) is induced in the cells following various stresses. However, the effect of recombinant protein expression on ROS generation has not been studied yet. In this study, H2O2 concentration and catalase activity variations and their correlation with cell growth following cytoplasmic expression of human interleukin-2 (hIL-2) and mouse interleukin-4 (mIL-4) in Escherichia coli Bl21(DH3) were investigated. Additionally, the effect of recombinant protein expression under different conditions was compared to the effect of foreign DNA introduction on these factors. Plasmids pEThIL-2 and pETmIL-4 were used for expression of human interleukin-2 (hIL-2) and mouse interleukin-4 (mIL-4) inside the cytoplasm of the cells. Having confirmed protein expression, H2O2 concentration and catalase activity were measured at various ODs. Also, Hydrogen peroxide concentration was measured in interleukin-4 expressing and wild type cells which treated with different concentrations of IPTG. Empty vector introduction increased significantly H2O2 concentration of the cells. However, H2O2 concentration in hIL-2 and mIL-4 expressing cells was significantly higher than its concentration in empty vector transformed cells. Catalase activity was reduced in foreign DNA introduced cells. It was more lowered following expression of recombinant proteins. Results of this study revealed the relationship between foreign DNA introduction and protein expression with H2O2 elevation and catalase activity reduction. There was also correlation between H2O2 elevation and reduction in catalase activity with the cell growth depression and recombinant protein production amount.