Sequencing, cloning and expression of DnaK chaperone from Bacillus halodurans Guj1

Hsp70 family members are central components of the cellular network of molecular chaperones and folding catalysts. The gene encoding a protein related to Hsp70 or DnaK in the domain bacteria is called dnaK. DnaK proteins are involved in de novo protein folding, formation, and disassembly of protein complexes and degradation of misfolded proteins. The gene dnaJ which codes for Hsp40 in bacteria, modulate the activities of DnaK by acting as co-chaperone. In the present study, we cloned and expressed DnaK from Bacillus halodurans Guj1 were identified. The dnaK gene of B. halodurans was successfully expressed in E. coli BL21 (DE3) using pET-28a+ expression system. The open reading frame of the cloned gene contained 1839bp and encoded 612 amino acid residues. Calculated molecular weight and pI of the protein were 66.18kDa and 4.55 respectively. The deduced amino acid sequence of B. halodurans Guj1 showed about 60% identity with the E. coli counterpart. The 3D structure of dnaK from B. halodurans was constructed using the crystal structure of human HSP70 chaperone BiP as the template, which showed an identity of 88.8% together. Partially purified recombinant DnaK by heat treatment showed a band at approximately 70kDa on SDS-PAGE. Our findings showed that the recombinant DnaK improved the refolding efficiency of the carbonic anhydrase by 27% after 60min at 54°C. According to the results obtained, DnaK from B. halodurans can potentially be used for improving the functional properties of enzymes and proteins in various applications.