RESUMO
@#Objective To express the molecular chaperone Acr2 protein of Mycobacterium tuberculosis(Mtb)in E.coli and analyze the function. Methods The recombinant plasmid pET-28a-Acr2 was transformed into competent E. coli BL21(DE3),and induced by IPTG. The expressed His-Acr2 protein was purified by Ni-NTA chromatography and SuperdexTM200 10/300 GL gel filtration chromatography to obtain Acr2 protein. The Acr2 protein was refolded by spontaneous refolding and reassembly after thermal denaturation(100 ℃ for 15 min)and chemical denaturation(8 mol/L urea,37 ℃ for 4 h).The secondary structure of Acr2 protein before and after denaturation-renaturation was detected by circular dichroism spectroscopy and non-denaturing SDS-PAGE,and the molecular chaperone function of Acr2 protein in vitro was detected by substrate binding assay. Results The purified Acr2 protein had the relative molecular mass of about 232 000,the purity of over 90%,and the concentration of about 2 mg/mL,which recovered its natural secondary structure after denaturationrenaturation,and formed stable complexes with the denatured malate dehydrogenase(MDH)at 48 ℃. Conclusion The Acr2protein can restore its natural molecular conformation with molecular chaperone activity in vitro after denaturation-renaturation treatment,providing a new strategy for the preparation of Mtb protein antigen with natural activity.