Mycobacterium tuberculosis HspX/EsxS Fusion Protein: Gene Cloning, Protein Expression, and Purification in Escherichia coli

Background: The purpose of this study was to clone, express, and purify a novel multidomain fusion protein of Micobacterium tuberculosis (Mtb) in a prokaryotic system. Methods: An hspX/esxS gene construct was synthesized and ligated into a pGH plasmid, E. coli TOP۱۰ cells were transformed, and the vector was purified. The vector containing the construct and pET-۲۱b (+) plasmid were digested with the same enzymes and the construct was ligated into pET-۲۱b (+). The accuracy of cloning was confirmed by colony PCR and sequencing. E. coli BL۲۱ cells were transformed with the pET-۲۱b (+)/hspX/esxS expression vector and protein expression was evaluated. Finally, the expressed fusion protein was purified on a Ni-IDA column and verified by SDS-PAGE and western blotting. Results: The hspX/esxS gene construct was inserted into pET-۲۱b (+) and recombinant protein expression was induced with IPTG in E. coli BL۲۱ cells. Various concentrations of IPTG were tested to determine the optimum concentration for expression induction. The recombinant protein was expressed in insoluble inclusion bodies. Three molar guanidine HCl was used to solubilize the insoluble protein. Conclusions: An HspX/EsxS Mtb fusion protein was expressed in E. coli and the recombinant protein was purified. After immunological analysis, the HspX/EsxS fusion protein might be an anti-tuberculosis vaccine candidate in future clinical trial studies.

Keywords:

Mycobacterium tuberculosis , HspX/ EsxS fusion protein , Gene cloning , Protein expression , Protein purification