Interaction of the Hsp70 molecular chaperone, DnaK, with its cochaperone DnaJ

AUTOR(ES)

Suh, Won-Chul

FONTE

The National Academy of Sciences

RESUMO

Chaperones of the Hsp70 family bind to unfolded or partially folded polypeptides to facilitate many cellular processes. ATP hydrolysis and substrate binding, the two key molecular activities of this chaperone, are modulated by the cochaperone DnaJ. By using both genetic and biochemical approaches, we provide evidence that DnaJ binds to at least two sites on the Escherichia coli Hsp70 family member DnaK: under the ATPase domain in a cleft between its two subdomains and at or near the pocket of substrate binding. The lower cleft of the ATPase domain is defined as a binding pocket for the J-domain because (i) a DnaK mutation located in this cleft (R167H) is an allele-specific suppressor of the binding defect of the DnaJ mutation, D35N and (ii) alanine substitution of two residues close to R167 in the crystal structure, N170A and T173A, significantly decrease DnaJ binding. A second binding determinant is likely to be in the substrate-binding domain because some DnaK mutations in the vicinity of the substrate-binding pocket are defective in either the affinity (G400D, G539D) or rate (D526N) of both peptide and DnaJ binding to DnaK. Binding of DnaJ may propagate conformational changes to the nearby ATPase catalytic center and substrate-binding sites as well as facilitate communication between these two domains to alter the molecular properties of Hsp70.

Documentos Relacionados

• Mutations in the DnaK chaperone affecting interaction with the DnaJ cochaperone
• A molecular chaperone, ClpA, functions like DnaK and DnaJ.
• Its substrate specificity characterizes the DnaJ co-chaperone as a scanning factor for the DnaK chaperone
• The ATP hydrolysis-dependent reaction cycle of the Escherichia coli Hsp70 system DnaK, DnaJ, and GrpE.
• DnaK, DnaJ and GrpE form a cellular chaperone machinery capable of repairing heat-induced protein damage.