A functional DnaK dimer is essential for the efficient interaction with Hsp40 heat shock protein

Area of Science:

• Molecular Biology
• Protein Biochemistry
• Structural Biology

Background:

• Heat shock proteins (Hsp70s) are vital molecular chaperones maintaining protein homeostasis.
• DnaK from Escherichia coli is a model Hsp70 extensively studied for its functions.
• ATP binding regulates DnaK oligomerization, shifting equilibrium from oligomers to monomers.

Purpose of the Study:

• To investigate the functional significance of the DnaK-ATP dimer structure.
• To elucidate the role of DnaK dimerization in chaperone activity and co-chaperone interactions.

Main Methods:

• Crystal structure determination of DnaK in complex with ATP.
• Biochemical analyses including solution dimer formation assays.
• Cross-linking experiments to confirm ATP-dependent dimer formation.
• Site-directed mutagenesis of dimer interface residues.

Main Results:

• DnaK forms a specific dimer in an ATP-dependent manner.
• Mutations at the dimer interface compromised DnaK's chaperone activity and dimer formation.
• Dimer formation is essential for efficient interaction with the Hsp40 co-chaperone.
• Intrinsic activities and GrpE co-chaperone interaction were largely unaffected by mutations.

Conclusions:

• DnaK undergoes transient dimerization upon ATP binding.
• This DnaK dimer is critical for effective Hsp40 co-chaperone engagement.
• Dimerization represents a key regulatory mechanism for DnaK function in proteostasis.