Abstract
Molecular chaperone DnaK, cooperating with DnaJ and GrpE, has ATPase activity and functions in diverse cellular functions. In the cyanobacterium Synechococcus elongatus PCC 7942 (here after referred as S. 7942), three dnaK homologues (dnaK1, dnaK2, dnaK3) and four dnaJ homologues (dnaJ1, dnaJ2, dnaJ3, dnaJ4) have been identified. DnaK and DnaJ homologues in S. 7942 exhibit distinct dispensability, expression profiles, and localizations, suggesting that each DnaK and DnaJ proteins plays distinct roles in the S. 7942 cells.
In order to reveal the partnership between three DnaK and four DnaJ proteins in vitro, each recombinant DnaK, DnaJ and GrpE protein was purified and the DnaK ATPase activity was compared among the combinations with DnaJ and GrpE by malachite green assay. Among three DnaK proteins, DnaK2 showed the highest ATPase activity. In addition, the ATPase activity in each DnaK was enhanced by the addition of DnaJ and/or GrpE. In case of DnaK1 and DnaK2, the activity was most enhanced by DnaJ2, whereas the activity of DnaK3 was most enhanced by DnaJ3.
