Cloning, prokaryotic expression, and functional characterization of a novel 70-kDa heat shock protein (DnaK) from Bacillus persicus

摘要

The dnaK gene of Bacillus persicus strain B48(T) was cloned, sequenced, and functionally characterized in the present study. The gene was 1836 bp in length, encoding a polypeptide of 611 amino acid residues. The 3D structure of protein predicted by I-TASSER represented the similarity of the overall structures of DnaK from B. persicus strain B48(T) and human protein Hsp70 (BiP) with a homology of 89 %. Based on the results, refolding heat-denatured carbonic anhydrase increased significantly up to 80 % in the presence of the purified recombinant DnaK. In addition, salt resistance experiments demonstrated a 2.7-fold increase in the survival of recombinant E. coli BL21-DnaK in the presence of 0.4 M NaCl for 60 h compared to that of the control cells. Further, Cd2+ failed to affect DnaK refolding function, while Hg2+ ion reflected a biphasic effect (inhibiting and stimulating at lower and higher than 100 nM concentrations, respectively). Finally, DnaK from B. persicus can potentially be used for improving the functional properties of enzymes and proteins through increasing folding activity and enhancing stress tolerance.