# GrpE
**GrpE** (for GroP-like gene E) is a bacterial co-chaperone protein that acts as the nucleotide exchange factor (NEF) for DnaK, the principal Hsp70 molecular chaperone of *Escherichia coli*. It promotes the dissociation of adenosine diphosphate (ADP) from the nucleotide-binding cleft of DnaK, allowing ATP to bind and complete one turn of the chaperone's protein-folding cycle.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) Homologs of GrpE operate in the mitochondria and chloroplasts of eukaryotic cells, while the eukaryotic cytosol uses structurally unrelated exchange factors instead.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
| Key fact | Detail |
|---|---|
| Function | Nucleotide exchange factor for the Hsp70 chaperone DnaK; stimulates ADP release about 5000-fold, enabling ATP rebinding and substrate release[2](https://www.ebi.ac.uk/interpro/entry/interpro/IPR000740) |
| Discovery | Identified in 1977 in a genetic screen for *E. coli* mutants that failed to propagate bacteriophage λ (Saito and Uchida)[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) |
| Genetic status | Essential for *E. coli* growth at all temperatures; expression induced by heat shock through the σ70 and σ32 promoters[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) |
| Structure | Asymmetric homodimer; each monomer has an N-terminal disordered segment, long coiled-coil α-helices forming a four-helix bundle, and a C-terminal β-sheet domain[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) |
| Binding interface | The GrpE–DnaK ATPase-domain interface buries over 2800 Ų of surface; reported dissociation constants are 30 nM (surface plasmon resonance) and 1 nM (transient kinetics)[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) |
| Thermosensor | The coiled-coil domain begins melting near physiological temperature, with a melting midpoint of about 48–50 °C, reducing exchange activity during heat shock[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC10825016/) • [1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) |
| Eukaryotic homologs | Mitochondrial GrpE-like proteins (Mge1p in yeast; GrpEL1 and GrpEL2 in vertebrates) and chloroplast homologs; the cytosol instead uses BAG-domain and Hsp110 exchange factors[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC12987570/) |
## Role in the DnaK chaperone cycle
DnaK couples cycles of ATP binding, hydrolysis, and ADP release by its N-terminal nucleotide-binding domain (NBD) to the sequestration and release of unfolded proteins by its C-terminal substrate-binding domain. ATP hydrolysis is stimulated by the co-chaperone DnaJ, after which DnaK enters a long-lived ADP-bound state that holds substrate tightly. GrpE closes the cycle: it binds the ADP-bound NBD, opens the nucleotide-binding cleft, and allows ADP to dissociate so that ATP can rebind, which triggers release of the substrate protein.[2](https://www.ebi.ac.uk/interpro/entry/interpro/IPR000740) • [1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
Kinetic measurements show that GrpE accelerates ADP release from DnaK 5000-fold through an associative displacement mechanism, in which an initial collision complex between GrpE and DnaK·ADP undergoes an isomerization that results in nucleotide release.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) The thermodynamic coupling works in each direction: GrpE weakens DnaK's binding of ADP two hundredfold, while ADP likewise weakens GrpE's binding of DnaK by the same factor of 200.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) GrpE also augments peptide release from the DnaK substrate-binding domain, an activity attributed to its N-terminal region, and a 2025 study identified the DnaK-binding motif in these disordered N-terminal tails as 17IIM19, conserved across many bacterial species.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) • [5](https://pubmed.ncbi.nlm.nih.gov/41279868/)
## Structure and exchange mechanism
The first high-resolution view came from the 1997 crystal structure of N-terminally truncated GrpE bound to the ATPase domain of DnaK (PDB entry 1DKG). GrpE is an asymmetric dimer bent toward the ATPase domain, with the β-sheet domain of the proximal monomer wedged into the mouth of the nucleotide-binding cleft.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) The interface buries over 2800 Ų of surface area, consistent with the high affinity of the complex.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
**A wedge, not a grip.** GrpE does not directly contact the nucleotide itself; the closest approach of any GrpE side chain to the nucleotide-binding pocket is about 15 Å. Instead, binding forces a rigid-body motion of DnaK domain IIB outward by 14°, disrupting three side-chain contacts to the adenine and ribose rings of the nucleotide and causing dissociation.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) This places GrpE among exchange factors that open the nucleotide-binding cleft by displacing subdomain IIB, a mechanism shared with eukaryotic BAG-domain proteins and Hsp110s but distinct from HspBP1, which displaces lobe I instead.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC2575452/) A DnaK-specific extended loop at the top of domain IIB is required for GrpE binding; GrpE neither binds to nor stimulates nucleotide release from cytosolic Hsp70s or the bacterial Hsp70-like protein HscA, which lack this loop.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
A later crystal structure of the *Geobacillus kaustophilus* DnaK–GrpE complex captured two DnaK molecules bound to one GrpE dimer, and a 2024 structure of the *Mycobacterium tuberculosis* DnaK–GrpE complex, whose DnaK is essential for viability of that pathogen, extended the structural picture to nearly full-length components.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC4400324/) • [8](https://pubmed.ncbi.nlm.nih.gov/38253530/)
## Thermosensor function
GrpE activity decreases at temperatures relevant to heat shock, showing non-Arrhenius behavior: the exchange rate rises less with temperature than expected, or falls. Thermodynamic analyses of *E. coli* GrpE revealed two thermal transitions, one assigned to the long α-helices with a midpoint near 50 °C, within the heat-shock range, and a second near 75 °C assigned to the four-helix bundle and β-domains.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) The coiled-coil domain unfolds with a melting temperature of 48 °C, so above the normal physiological temperature for *E. coli* (37 °C) GrpE begins to melt, loses exchange function, and DnaK remains in the ADP-bound, high-substrate-affinity conformation.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC10825016/) The effect is fully reversible as temperature decreases.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) GrpE homologs from thermophilic bacteria show the same behavior at temperatures matching their own growth ranges, and thermosensory function appears to be preserved in eukaryotic organelles.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) • [9](https://pmc.ncbi.nlm.nih.gov/articles/PMC4753570/)
## Distribution and eukaryotic homologs
GrpE is the ubiquitous exchange factor in bacteria, and protein folding by DnaK in *E. coli* depends on it, since grpE is an essential gene.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC4753570/) • [1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/) [Mitochondria](https://www.edgepedia.org/mitochondria) and chloroplasts, organelles of eubacterial origin, retain GrpE homologs, and protein folding within these organelles depends on GrpE function.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC4753570/) The yeast mitochondrial homolog Mge1p is essential for viability and acts as an exchange factor for the mitochondrial matrix Hsp70 Ssc1p, though unlike GrpE it is not heat inducible; GrpE and Mge1p share only 34% amino acid identity.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
During eukaryotic evolution GrpE was lost from the cytosol and replaced by unrelated exchange factor families, chiefly Hsp110, HspBP1/Sil1, and BAG-domain proteins, all of which target subdomain IIB of the Hsp70 nucleotide-binding domain.[10](https://www.sciencedirect.com/science/article/pii/S0021925825023002) • [9](https://pmc.ncbi.nlm.nih.gov/articles/PMC4753570/) In vertebrates, two mitochondrial GrpE-like paralogs exist: GrpEL1, found throughout higher eukaryotes, and GrpEL2, whose concurrent expression with GrpEL1 is specific to vertebrates such as mouse, zebrafish, and human. The human paralogs share 42% sequence identity, and human GrpEL1 binds ADP-bound mitochondrial Hsp70 with approximately 10-fold higher affinity than GrpEL2, suggesting a preferred exchange factor in the mitochondrial matrix.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC12987570/)
## References
1. [Harrison C (2003). GrpE, a nucleotide exchange factor for DnaK. Cell Stress & Chaperones 8(3):218–224.](https://pmc.ncbi.nlm.nih.gov/articles/PMC514874/)
2. [GrpE nucleotide exchange factor (IPR000740), InterPro, EMBL-EBI.](https://www.ebi.ac.uk/interpro/entry/interpro/IPR000740)
3. [New insights into the structure and function of the complex between the Escherichia coli Hsp70, DnaK, and its nucleotide-exchange factor, GrpE. PMC (2024).](https://pmc.ncbi.nlm.nih.gov/articles/PMC10825016/)
4. [Tuning the Hsp70 chaperone cycle: emerging roles of GrpE-like nucleotide exchange factors in proteostasis and organelle function. Protein & Cell.](https://pmc.ncbi.nlm.nih.gov/articles/PMC12987570/)
5. [The nucleotide exchange factor, GrpE, modulates substrate affinity by interaction of its N-terminal tails with the DnaK substrate-binding domain. PubMed (2025).](https://pubmed.ncbi.nlm.nih.gov/41279868/)
6. [Insights into the structural dynamics of the Hsp110–Hsp70 interaction reveal the mechanism for nucleotide exchange activity. PMC.](https://pmc.ncbi.nlm.nih.gov/articles/PMC2575452/)
7. [Modulation of the Chaperone DnaK Allosterism by the Nucleotide Exchange Factor GrpE. PMC (2015).](https://pmc.ncbi.nlm.nih.gov/articles/PMC4400324/)
8. [Structure of the M. tuberculosis DnaK-GrpE complex reveals how key DnaK roles are controlled. PubMed (2024).](https://pubmed.ncbi.nlm.nih.gov/38253530/)
9. [Bracher A, Verghese J (2015). The nucleotide exchange factors of Hsp70 molecular chaperones. Frontiers in Molecular Biosciences.](https://pmc.ncbi.nlm.nih.gov/articles/PMC4753570/)
10. [Hsp110 nucleotide exchange factors may amplify Hsp70-disaggregation by enhanced entropic pulling. Journal of Biological Chemistry 301(8) (2025).](https://www.sciencedirect.com/science/article/pii/S0021925825023002)
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*Topic: Encyclopedia › Life and health › Biological foundations › Biochemistry and metabolism › Protein families and complexes › Structural, chaperone, and RNA-binding protein families › Chaperone and heat-shock protein families › Hsp110 and related nucleotide-exchange families*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license