Potassium ions and the molecular-chaperone activity of DnaK.

Potassium ions stabilize the DnaK.ADP complex that forms on incubation of nucleotide-free DnaK with ADP or ATP. Generation of the crystallographically defined Mg2+ cluster [Wilbanks, S.M. & McKay, D.B. (1995) J. Biol. Chem. 270, 2251-2257], in which two K+ and the nucleotide are bound together with Mg2+ in the ATPase site, appears to be essential for the ATP-induced acceleration of binding of peptide ligands, the ATP-induced release of peptide ligands and for the peptide-induced increase in ATPase activity. Thus, K+ is instrumental in signal transmission between the ATPase site and the peptide-binding site.