Enhanced Expression and Solubility of Main Protease (Mpro) of SARS-CoV-2 from E. Coli

The COVID-19 pandemic has posed disastrous consequences for the world. Main protease (Mpro) of SARS-CoV-2 is a safe and promising target mainly because it is conserved across variants and has no overlap with human proteases. Large quantities of Mpro are required for the screening of different inhibitors effective against SARS-CoV-2. In the present study, Mpro of SARS-CoV-2 was successfully cloned and expressed in two E. coli hosts BL21-DE3 and BL21-DE3-RIL. The optimization of induction conditions and use of modified host helped improve the expression and solubility of Mpro in E. coli. Mpro was purified by affinity chromatography and high yields (> 35 mg per litre shaker flask culture) were recovered form BL21-DE3-RIL strain which was almost double that from BL21-DE3 strain. The purified Mpro was further characterized by for mass spectroscopy, fluorescence spectroscopy as well as circular dichroism. Thus, this can enable cost effective, high yield and rapid production of Mpro at industrial scale.