Abstract: Objective To clone and express the genes Rv3803c and Rv3846 from Mycobacterial tuberculosis in Escherichia coli cells, and to purify Rv3803c and Rv3846 proteins. Methods The genes Rv3803c and Rv3846 were amplified from Mycobacterial tuberculosis H37Rv genomic DNA by polymerase chain reaction (PCR). PCR products were cloned into the expression vector pGEX-6P-1. After the plasmids were sequenced and validated their correctness, the recombinant plasmids were transformed into E. coli Rosetta strain to induce the expression of proteins. The proteins were purified by the GST-tag affinity chromatography, and then electrophoresed, stained with Coomassic brilliant blue, identified by Western-blot. Results The sequences of recombinant plasmids pGEX-Rv3803c and pGEX-Rv3846 are consistent with the design. The proteins GST-Rv3803c and GST-Rv3846 existed 50% in the soluble fraction and 50% in the inclusion body of E. coli Rosetta. Their molecular weights were 56 000 and 45 000, respectively. The purities of final products were higher than 90%. The concentrations of the purified recombinant proteins were approximately 0.1 mg/ml and 0.5 mg/ml, respectively. The yields of the recombinant proteins GST-Rv3803c and GST-Rv3846 were 0.25 mg and 1.25 mg from per liter of the E. coli Rosetta cultures, respectively. Conclusion The purified proteins Rv3803c（MPT51）and Rv3846（SodA）were successfully obtained, which provide the experimental basis for the further study of auxiliary diagnostic value of MPT51 and SodA proteins and construction of protective vaccines.

Key words: Mycobacterium tuberculosis, Antigens,bacterial, Bacterial proteins, Superoxide dismutase