Functional characterisation of the chaperones DnaK, DnaJ and GrpE from Clostridium acetobutylicum

The DnaK chaperone system is involved in various cellular processes such as the control of the folded and oligomeric state of proteins under stress an d non-stress conditions. In this study we functionally characterised the ho mologues of the DnaK system from Clostridium acetobutylicum. DnaK, DnaJ, Gr pE and OrfA were heterologously synthesised in Escherichia coli and affinit y 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. ac etobutylicum DnaJ could stimulate the E. coli DnaK ATPase by a factor of 55 . Furthermore, the DnaK system from C. acetobutylicum was able to prevent t he aggregation of OrfA from C. acetobutylicum, which is similar to the repr essor HrcA of CIRCE-regulated heat shock genes in Bacillus subtilis. (C) 19 99 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.