DnaJ, Heat shock protein, functions in association with DnaK (Hsp70) molecular chaperone to facilitate protein folding. p70 chaperone. DnaJ plays a key role in the chaperone reaction by stimulating the ATPase activity and activating the substrate binding of Hsp70.. DnaJ consists of four domains that are N-terminal 76 amino acid J-domain, G/F domain, zinc-binding cystein rich CR-domain, C-terminal CTD-domain and they are conserved to various degrees among the homologues.