The DnaK/DnaJ/GrpE chaperone system is responsible for:
Hsp70 chaperone system DnaK-DnaJ-GrpE is highly conserved ATP-dependent folding machine from bacteria to humans. DnaK N-terminal ATPase domain linked to substrate-binding domain exists in ATP-bound low-affinity open state with rapid substrate exchange. DnaJ Hsp40 cochaperone with J-domain delivers unfolded proteins exposing hydrophobic patches and potently stimulates ATP hydrolysis via HPD motif interaction, converting DnaK to ADP-bound high-affinity closed state that tightly clamps onto extended segment of about seven residues enriched in leucine and isoleucine. GrpE dimeric nucleotide exchange factor binds DnaK and catalyzes ADP release allowing ATP rebinding and substrate discharge for another cycle or transfer to GroEL-ES chaperonin. During heat shock aggregated proteins accumulate; this machinery collaborates with ClpB disaggregase that threads aggregates through central pore, prevents irreversible inclusion bodies, resolubilizes existing foci and maintains proteome integrity. It does not catalyze DNA replication, membrane phospholipid synthesis or quorum sensing, but exclusively manages protein quality control under thermodynamic stress ensuring post-stress recovery.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 7: DnaK-DnaJ-GrpE Chaperone System in Protein Refolding.