Abstract
Human interferon-β Ser17 (IFN-βS17) is a variant of human fibroblast interferon-β in which cysteine 17 has been genetically replaced by serine. This form of human interferon-β was approved by the U.S. Food and Drug Administration for the treatment of multiple sclerosis and a number of pathological conditions. The expression of interferon-β in E. coli is hampered by both its toxicity to bacterial cells and its instability. Besides, many studies have shown that interferon-β expressed in E. coli is present in inclusion bodies as an insoluble protein. The extraction, denaturation, and renaturation of this protein into an active form is time-consuming and costly.In order to obtain soluble interferon-β protein directly by affinity chromatography, several fusion protein expression systems have been experimented in this study. We prepared two different IFN-βS17 fusion proteins by fusing IFN-βS17 gene to maltose-binding protein (MBP) gene or glutathione S-transferase (GST) gene and expressing them. Because of IFN-β’s instability and sensitivity to E. coli endogenous proteinase, several factors influencing protein maturation and solubility including incubation temperature and inducer concentrations, and host cells were investigated.In addition to expression levels, biological activities of the fusion proteins and the IFN-βS17 derived from them were compared. Both anti-viral and anti-growth assays were performed. The results indicated that fusion proteins were active in functional assays, and IFN-βS17 derived from the fusion proteins after factor Xa or thrombin cleavage possessed activities comparable to those of interferon-β produced by Chinese Hamster ovary cells.