DnaJ potentiates the interaction between DnaK and alpha-helical peptides.

Molecular chaperones bind selectively to nascent, unfolded, misfolded, or aggregated polypeptides, and are involved in protein folding, protein targeting to membranes, and protein renaturation after stress. The DnaK chaperone of Escherichia coli is known to interact preferentially with positively charged hydrophobic peptides in an extended conformation. Accordingly, we show in the present study that DnaK has a low affinity for alpha-helical peptides. In the presence of its co-chaperone DnaJ and ATP, however, DnaK interacts more efficiently with alpha-helical peptides. This suggests that DnaJ triggers a conformational change in DnaK which improves its interaction with these peptides. The ability of the DnaK/DnaJ/GrpE chaperone machine to interact with alpha-helical peptides (which represent the most frequent secondary structure in proteins) should be an important part of its role in protein folding and renaturation.