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, prot ein targeting to membranes, and protein renaturation after stress. The DnaK chaperone of Escherichia coli is known to interact preferentiall y with positively charged hydrophobic peptides in an extended conforma tion. Accordingly, we show in the present study that DnaK has a low af finity for alpha-helical peptides, In the presence of its co-chaperone DnaJ and ATP, however, DnaK interacts more efficiently with alpha-hel ical peptides. This suggests that DnaJ triggers a conformational chang e in DnaK which improves its interaction with these peptides. The abil ity of the DnaK/DnaJ/GrpE chaperone machine to interact with alpha-hel ical peptides (which represent the most frequent secondary structure i n proteins) should be an important part of its role in protein folding and renaturation.