dnaK

Gene Description

DnaK is the canonical bacterial Hsp70-family ATP-dependent molecular chaperone. It binds exposed hydrophobic segments of non-native polypeptides and, through repeated ATP-driven cycles of substrate binding and release, prevents aggregation and assists the (re)folding of proteins both co-translationally and post-translationally. The protein has the conserved Hsp70 architecture, comprising an N-terminal nucleotide-binding domain (NBD) that binds and hydrolyzes ATP, a substrate-binding domain (SBDbeta) that binds short peptide segments of client proteins, an alpha-helical lid (SBDalpha) that regulates substrate capture and release, and a short intrinsically disordered C-terminal tail. In the ATP-bound state DnaK has low substrate affinity and fast exchange, and ATP hydrolysis switches it to a high-affinity ADP state that stabilizes client binding. DnaK operates as part of the bacterial KJE chaperone system together with the J-domain co-chaperone DnaJ (Hsp40), which stimulates DnaK ATPase activity and delivers substrates, and the nucleotide-exchange factor GrpE, which promotes ADP release and substrate cycling. DnaK functions primarily in the cytoplasm and is a central component of the heat-shock and protein quality-control (proteostasis) network, with its expression induced by heat and other stresses.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005524 ATP binding	IEA GO_REF:0000120	ACCEPT	Summary: DnaK is an ATP-dependent Hsp70 chaperone whose N-terminal nucleotide-binding domain binds ATP; ATP binding and hydrolysis drive the chaperone cycle. ATP binding is well established for the Hsp70 family and supported by the conserved actin-like ASKHA nucleotide-binding domain fold of this protein. Reason: Core molecular function of an Hsp70 chaperone, strongly supported by family membership, conserved nucleotide-binding domain, and the canonical DnaK mechanism. The IEA evidence is appropriate and consistent with the biology. Supporting Evidence: PMID:33668424 ATP binding and hydrolysis by DnaK NBD allosterically controls the binding of SBD to its substrates—short hydrophobic peptide segments that would normally be buried in the folded structure.
GO:0006457 protein folding	IEA GO_REF:0000002	ACCEPT	Summary: DnaK assists folding of non-native polypeptides and prevents aggregation through ATP-driven cycles of substrate binding and release, acting in the cytoplasm as part of the DnaK-DnaJ-GrpE system. This is the central biological process for bacterial Hsp70. Reason: Core biological process for DnaK, well supported by family function and conserved domain architecture. Appropriately captured by an IEA annotation. Supporting Evidence: PMID:33668424 DnaK facilitates the folding through repeated cycles of ATP-dependent binding and release of an unfolded protein [6]. PMID:7937953 Several rounds of ATP-dependent interaction with DnaK and DnaJ are required for fully efficient folding.
GO:0016887 ATP hydrolysis activity	IEA GO_REF:0000002	ACCEPT	Summary: The DnaK nucleotide-binding domain catalyzes ATP hydrolysis, which is allosterically coupled to substrate binding in the substrate-binding domain; ATP hydrolysis (stimulated by DnaJ) switches DnaK to the high-affinity client-binding state. This ATPase activity is intrinsic to and definitional for the Hsp70 family. Reason: Core molecular function of DnaK that powers the chaperone cycle. Strongly supported by family membership and conserved catalytic NBD; the IEA annotation is appropriate. Supporting Evidence: PMID:33668424 ATP binding and hydrolysis by DnaK NBD allosterically controls the binding of SBD to its substrates—short hydrophobic peptide segments that would normally be buried in the folded structure.
GO:0140662 ATP-dependent protein folding chaperone	ISS PMID:7937953 The ATP hydrolysis-dependent reaction cycle of the Escherich...	NEW	Summary: Q88DU2 is canonical bacterial DnaK: its ATPase and substrate-binding domains drive repeated ATP-dependent client binding and release during protein folding. Direct E. coli DnaK/DnaJ/GrpE experiments establish the conserved foldase cycle, while the full-text P. putida study describes the same mechanism and shows that DnaK chaperone function affects GraT activity and competitive fitness. Reason: GO:0140662 is the evidence-matched current molecular function for an ATP-dependent Hsp70 foldase and is more specific than GO:0044183. ISS is used because direct reconstitution of folding was performed with E. coli DnaK (UniProtKB:P0A6Y8), recorded machine-readably in supporting_entities, whereas the KT2440-isogenic P. putida paper supports the conserved DnaK mechanism but does not directly reconstitute Q88DU2-mediated client refolding. GO:0051082 is not retained: it is obsolete, and client binding here is a mechanistic step in the ATP-dependent foldase cycle. A distinct holdase NTR would require context-specific evidence not established for Q88DU2 in the cached literature. Supporting Evidence: PMID:7937953 The binding and release of substrate protein for folding involves the following ATP hydrolysis-dependent cycle: (i) unfolded luciferase binds initially to DnaJ; (ii) upon interaction with luciferase-DnaJ, DnaK hydrolyzes its bound ATP, resulting in the formation of a stable luciferase-DnaK-DnaJ complex; (iii) GrpE releases ADP from DnaK; and (iv) ATP binding to DnaK triggers the release of substrate protein, thus completing the reaction cycle. PMID:33668424 DnaK facilitates the folding through repeated cycles of ATP-dependent binding and release of an unfolded protein [6].

Core Functions

ATP-dependent Hsp70 molecular chaperone that binds non-native polypeptides and, through ATP-binding and ATP-hydrolysis-driven cycles of substrate capture and release, prevents aggregation and assists protein folding as part of the DnaK-DnaJ-GrpE (KJE) system in the cytoplasm.

Molecular Function:

ATP-dependent protein folding chaperone

Directly Involved In:

protein folding

Supporting Evidence:

PMID:7937953
Several rounds of ATP-dependent interaction with DnaK and DnaJ are required for fully efficient folding.
PMID:33668424
DnaK facilitates the folding through repeated cycles of ATP-dependent binding and release of an unfolded protein [6].
PMID:33668424
ATP binding and hydrolysis by DnaK NBD allosterically controls the binding of SBD to its substrates—short hydrophobic peptide segments that would normally be buried in the folded structure.
file:PSEPK/dnaK/dnaK-deep-research-falcon.md
DnaK is the canonical bacterial Hsp70-family ATP-dependent molecular chaperone that supports proteostasis by binding non-native polypeptides and preventing aggregation, assisting folding through repeated ATP-driven binding/release cycles, operating with co-chaperones DnaJ and GrpE.

Gene Description

Existing Annotations Review

Core Functions

ATP-dependent Hsp70 molecular chaperone that binds non-native polypeptides and, through ATP-binding and ATP-hydrolysis-driven cycles of substrate capture and release, prevents aggregation and assists protein folding as part of the DnaK-DnaJ-GrpE (KJE) system in the cytoplasm.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

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Notes

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