In prokaryotes, the nucleotide exchange factor GrpE and the chaperone DnaJ are required for nucleotide binding of the molecular chaperone DnaK PMID:9103205. The DnaK reaction cycle involves rapid peptide binding and release, which is dependent upon nucleotide binding. DnaJ accelerates the hydrolysis of ATP by DnaK, which enables the ADP-bound DnaK to tightly bind peptide. GrpE catalyses the release of ADP from DnaK, which is required for peptide release. In eukaryotes, GrpE is essential for mitochondrial Hsp70 function, however the cytosolic Hsp70 homologues are GrpE-independent.

GrpE binds as a homodimer to the ATPase domain of DnaK, and may interact with the peptide-binding domain of DnaK. GrpE accomplishes nucleotide exchange by opening the nucleotide-binding cleft of DnaK. GrpE is comprised of two domains, the coiled coil domain, which may facilitate peptide release, and the head domain, which forms part of the contact surface with the ATPase domain of DnaK. This entry represents the coiled-coil domain.