The Escherichia Coli DnaK Chaperone, the 70-kDa Heat Shock Protein Eukaryotic Equivalent, Changes Conformation Upon ATP Hydrolysis, Thus Triggering Its Dissociation from a Bound Target Protein

The DnaK protein of Escherichia coli and its eukaryotic hsp70 analogues are known to bind some polypeptides and to release or dissociate from them following ATP hydrolysis. Here we demonstrate that hydrolysis (and not simply binding) of nucleotide triphosphates leads to a change in the DnaK protein, from the "closed" to the "open" conformation. A conformational change is not observed with the mutant DnaK756 protein, which is always found in the open conformation. Although ATP is the preferred substrate, the hydrolysis of CTP, GTP, UTP, and dATP also results in DnaK's conversion from a closed to an open conformation. The ability of DnaK to hydrolyze various triphosphates correlates perfectly with its ability to release the bound denatured bovine pancreatic trypsin inhibitor polypeptide.