Elastin-like polypeptide fusions enhance transient expression of human IFN-γ in tobacco leaves

Abstract

The production of recombinant proteins for medical and industrial uses is widely enhanced in plants and transient expression systems have made much progress in recent years. However, low yield of production and the lack of suitable purification methods for recovering of recombinant proteins has led to develop different fusion protein strategies such as elastin-like polypeptide (ELP) fusions. In this study, the ELP sequence was fused to human interferon-γ (hIFN-γ) and transiently expressed in Nicotiana tabacum plants by Agroinfiltration. The ELP fusion significantly increased the accumulation of hIFN-γ by 2.6-fold with a high expression at an average of 22.48% of total soluble protein (TSP). The analysis of different salt concentrations on the recovery of the hIFN-γ-ELP revealed that recovery amount of the fusion protein was dependent on the NaCl concentration, with increase of NaCl concentration, a greater fraction of the hIFN-γ-ELP was aggregated. Furthermore, three rounds of Inverse Transition Cycling (ITC) purification increased overall purity of the hIFN-γ-ELP to 98 ± 2%. ITC was also used to separate hIFN-γ from ELP after cleavage of the fusion protein by Enterokinase. In addition, the in vitro bioassay indicated that ELP has no interfering effect on folding and biological activity of hIFN-γ.