Functional characterisation of the chaperones DnaK, DnaJ and GrpE fromClostridium acetobutylicum

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Abstract
The DnaK chaperone system is involved in various cellular processes such as the control of the folded and oligomeric state of proteins under stress and non-stress conditions. In this study we functionally characterised the homologues of the DnaK system from Clostridium acetobutylicum. DnaK, DnaJ, GrpE and OrfA were heterologously synthesised in Escherichia coli and affinity purified via a His-tag. By optimising the stoichiometry, we were able to refold guanidinium hydrochloride-denatured firefly luciferase in vitro with 22% of the yield obtained with the E coli DnaK system. In addition, C acetobutylicum DnaJ could stimulate the E coli DnaK ATPase by a factor of 55. Furthermore, the DnaK system from C acetobutylicum was able to prevent the aggregation of OrfA from C acetobutylicum, which is similar to the repressor HrcA of CIRCE-regulated heat shock genes in Bacillus subtilis.