id: Q88DU3
gene_symbol: dnaJ
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:160488
  label: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950
    / KT2440)
description: DnaJ (Hsp40) is the J-domain co-chaperone of the DnaK (Hsp70) chaperone
  system. It binds unfolded and misfolded substrate proteins and, through its N-terminal
  J domain, stimulates the ATPase activity of DnaK, driving the formation of a stable
  DnaK-substrate complex; the nucleotide-exchange factor GrpE then releases ADP from
  DnaK and ATP rebinding releases the substrate, completing an iterative folding cycle.
  DnaJ also has an autonomous, DnaK-independent holdase/chaperone activity that prevents
  the aggregation of stress-denatured proteins and helps disaggregate them. It is a
  cytoplasmic homodimer that coordinates two structural zinc ions per monomer through
  a cysteine-rich (CR-type) zinc-finger domain; zinc center 1 supports the autonomous
  chaperone activity and zinc center 2 is required for interaction with DnaK. Together
  with DnaK and GrpE, DnaJ mediates the cellular response to heat and hyperosmotic
  stress, promotes protein folding, refolding and disaggregation, and participates
  in the activation of replication-initiation proteins during plasmid and phage DNA
  replication.
existing_annotations:
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: This annotation is incorrect. DnaJ does not itself bind or hydrolyze ATP;
      it is a co-chaperone that stimulates the ATPase activity of its partner DnaK
      (Hsp70). It is DnaK, not DnaJ, that binds and hydrolyzes ATP. The UniProt record
      lists no ATP-binding site or feature for DnaJ, and there is no Walker motif in
      the sequence. This is a known erroneous InterPro2GO propagation to the DnaJ family
      and should be removed.
    action: REMOVE
    reason: DnaJ has no ATP-binding site or Walker motif in its sequence; ATP binding
      and hydrolysis are properties of its partner DnaK, so this is an erroneous family-level
      InterPro2GO transfer.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: with the DnaJ-bound protein, DnaK hydrolyzes its bound ATP, resulting
    - reference_id: file:PSEPK/dnaJ/dnaJ-notes.md
      supporting_text: DnaJ does NOT itself bind/hydrolyze ATP. It stimulates the ATPase
        activity of DnaK; the ATP-binding partner is DnaK.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Correct subcellular localization. UniProt assigns DnaJ to the cytoplasm,
      where it acts together with DnaK and GrpE on cytoplasmic substrate proteins.
    action: ACCEPT
    reason: The curated UniProt subcellular location places DnaJ in the cytoplasm,
      consistent with its action on cytoplasmic substrate proteins.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm'
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: Correct and a core biological process. As the J-domain co-chaperone of
      the DnaK system, DnaJ delivers unfolded substrates to DnaK and drives iterative
      ATP-dependent folding cycles, and it also has autonomous chaperone activity that
      prevents aggregation of stress-denatured proteins.
    action: ACCEPT
    reason: Protein folding is a direct, core biological process for this J-domain
      co-chaperone of the DnaK folding cycle.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: interactions between DnaJ, DnaK and GrpE are required for fully
- term:
    id: GO:0008270
    label: zinc ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000104
  qualifier: enables
  review:
    summary: Correct and specific. DnaJ binds two structural Zn(2+) ions per monomer
      through its cysteine-rich (CR-type) zinc-finger domain (eight coordinating Cys
      residues). Zinc center 1 supports the autonomous chaperone activity and zinc
      center 2 is required for interaction with DnaK. This is a specific metal-ion term
      (no broad 'metal ion binding' annotation is present in this GOA to down-rank).
    action: ACCEPT
    reason: Zinc binding is specific and structurally essential (two CR-type zinc centers
      required for chaperone activity and DnaK interaction); no broader metal-ion term
      is present to supersede it.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: Binds 2 Zn(2+) ions per monomer.
    - reference_id: file:PSEPK/dnaJ/dnaJ-notes.md
      supporting_text: Zinc center 1 plays an important role in the autonomous, DnaK-independent
        chaperone activity of DnaJ. Zinc center 2 is essential for interaction with
        DnaK and for DnaJ activity.
- term:
    id: GO:0009408
    label: response to heat
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: Correct and a core biological process. DnaJ participates actively in the
      response to heat shock (and hyperosmotic stress) by preventing the aggregation
      of stress-denatured proteins and disaggregating them, as part of the DnaK/DnaJ/GrpE
      heat-shock chaperone machinery.
    action: ACCEPT
    reason: DnaJ is a core component of the DnaK/DnaJ/GrpE heat-shock machinery that
      prevents and reverses heat-induced protein aggregation.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: heat shock by preventing the aggregation of stress-denatured proteins
- term:
    id: GO:0031072
    label: heat shock protein binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: The essence is correct - DnaJ physically binds DnaK, which is an Hsp70
      heat-shock protein. However, 'heat shock protein binding' is imprecise; the more
      informative term 'protein-folding chaperone binding' (GO:0051087) better captures
      the defining co-chaperone interaction with the DnaK chaperone that DnaJ stimulates.
    action: MODIFY
    reason: The interaction is real but 'heat shock protein binding' is imprecise; 'protein-folding
      chaperone binding' specifically captures the defining DnaK (Hsp70) co-chaperone
      interaction that DnaJ stimulates.
    proposed_replacement_terms:
    - id: GO:0051087
      label: protein-folding chaperone binding
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: with the DnaJ-bound protein, DnaK hydrolyzes its bound ATP, resulting
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: is essential for interaction with DnaK and for DnaJ activity
- term:
    id: GO:0042026
    label: protein refolding
  evidence_type: IEA
  original_reference_id: GO_REF:0000118
  qualifier: involved_in
  review:
    summary: Correct and a core biological process. Through repeated ATP-dependent
      cycles with DnaK and GrpE, and via its autonomous disaggregation activity, DnaJ
      promotes the refolding of denatured proteins to the native state.
    action: ACCEPT
    reason: Refolding of denatured proteins, via DnaK-coupled ATP-dependent cycles and
      autonomous disaggregation, is a direct, core biological process for DnaJ.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: and by disaggregating proteins, also in an autonomous, DnaK-independent
- term:
    id: GO:0001671
    label: ATPase activator activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: Proposed new core annotation. DnaJ's defining molecular function is not
      captured by the current GOA. Via its J domain, DnaJ binds to and stimulates the
      intrinsic ATPase activity of the DnaK (Hsp70) chaperone, driving stable substrate
      capture. This ATPase activator activity is annotated to Hsp40 proteins in Reactome
      (HSP40s activate intrinsic ATPase activity of HSP70s) and is the most informative
      molecular function for this co-chaperone.
    action: NEW
    reason: ATPase activator activity is the defining, most informative molecular function
      of this J-domain co-chaperone and is missing from the current GOA.
    supported_by:
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: The J domain is necessary and sufficient to stimulate DnaK
    - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
      supporting_text: PANTHER; PTHR43096:SF48; CHAPERONE PROTEIN DNAJ
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings:
  - statement: InterPro2GO correctly associates DnaJ with protein folding, response
      to heat, and chaperone-binding functions, but incorrectly transfers an ATP-binding
      term to the DnaJ family - DnaJ is a co-chaperone that stimulates DnaK's ATPase
      rather than binding ATP itself.
- id: GO_REF:0000104
  title: Electronic Gene Ontology annotations created by transferring manual GO annotations
    between related proteins based on shared sequence features
  findings:
  - statement: UniRule correctly transfers zinc ion binding, consistent with the two
      structural Zn(2+) ions coordinated by the CR-type zinc finger.
- id: GO_REF:0000118
  title: TreeGrafter-generated GO annotations
  findings:
  - statement: TreeGrafter correctly propagates protein refolding from the DnaJ/Hsp40
      family tree.
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings:
  - statement: Combined methods correctly assign cytoplasmic localization for this
      soluble chaperone.
- id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
  title: UniProt entry Q88DU3 (DNAJ_PSEPK)
  findings:
  - statement: DnaJ participates in the response to heat and hyperosmotic shock by
      preventing aggregation of stress-denatured proteins and disaggregating them,
      including in an autonomous, DnaK-independent fashion.
  - statement: Unfolded proteins bind initially to DnaJ; interaction with the DnaJ-bound
      substrate triggers DnaK to hydrolyze ATP and form a stable complex, with GrpE
      and ATP rebinding completing the iterative folding cycle.
  - statement: DnaJ is a cytoplasmic homodimer that binds two structural Zn(2+) ions
      per monomer; the J domain is necessary and sufficient to stimulate DnaK ATPase
      activity, and the two zinc centers have distinct roles in autonomous chaperone
      activity and DnaK interaction.
- id: file:PSEPK/dnaJ/dnaJ-notes.md
  title: Curator notes for dnaJ (Q88DU3)
  findings:
  - statement: The ATP binding annotation is an erroneous InterPro2GO propagation to
      the DnaJ family; DnaJ stimulates DnaK's ATPase but does not itself bind ATP,
      and should have this term removed.
  - statement: 'Heat shock protein binding (GO:0031072) is vague; the co-chaperone
      interaction with DnaK is better captured by protein-folding chaperone binding
      (GO:0051087).'
- id: file:interpro/panther/PTHR43096/PTHR43096-metadata.yaml
  title: PANTHER family PTHR43096 (DnaJ homolog 1, mitochondrial-related) and subfamily
    PTHR43096:SF48 (chaperone protein DnaJ)
  findings:
  - statement: UniProt classifies dnaJ (Q88DU3) in PANTHER family PTHR43096 and subfamily
      PTHR43096:SF48 (CHAPERONE PROTEIN DNAJ), confirming its assignment as a DnaJ/Hsp40
      co-chaperone.
  - statement: The PTHR43096:SF48 subfamily classification corroborates the J-domain
      co-chaperone identity used to support the ATPase activator and chaperone-binding
      functions in this review.
core_functions:
- description: DnaJ binds unfolded and misfolded substrate proteins and, via its J
    domain, stimulates the ATPase activity of the DnaK (Hsp70) chaperone, driving
    capture of the substrate and powering iterative ATP-dependent folding cycles
    with GrpE.
  molecular_function:
    id: GO:0001671
    label: ATPase activator activity
  directly_involved_in:
  - id: GO:0006457
    label: protein folding
  locations:
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
    supporting_text: The J domain is necessary and sufficient to stimulate DnaK
- description: DnaJ recognizes and binds unfolded/stress-denatured substrate proteins
    and, both autonomously and in cooperation with the DnaK/GrpE system, prevents
    their aggregation and promotes their refolding to the native state during heat
    and hyperosmotic stress.
  molecular_function:
    id: GO:0051087
    label: protein-folding chaperone binding
  directly_involved_in:
  - id: GO:0042026
    label: protein refolding
  - id: GO:0009408
    label: response to heat
  locations:
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
    supporting_text: and by disaggregating proteins, also in an autonomous, DnaK-independent
- description: DnaJ coordinates two structural Zn(2+) ions per monomer through its
    cysteine-rich (CR-type) zinc-finger domain; zinc center 1 supports autonomous
    chaperone activity and zinc center 2 is required for interaction with DnaK.
  molecular_function:
    id: GO:0008270
    label: zinc ion binding
  locations:
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: file:PSEPK/dnaJ/dnaJ-uniprot.txt
    supporting_text: Binds 2 Zn(2+) ions per monomer.
proposed_new_terms: []
suggested_questions:
- question: Does the autonomous, DnaK-independent holdase/disaggregation activity of
    DnaJ contribute measurably to proteostasis and stress survival in Pseudomonas putida,
    or is essentially all of its in vivo function mediated through DnaK?
- question: What is the substrate spectrum of DnaJ in P. putida under the solvent,
    oxidative, and heat stresses relevant to its environmental and biotechnological
    niche, and how does it compare with the well-characterized E. coli ortholog?
- question: How is dnaJ expression coordinated with the rpoH/sigma-32 heat-shock regulon
    and with dnaK/grpE in P. putida, and is it co-transcribed in a conserved operon?
suggested_experiments:
- experiment_type: Gene knockout and stress survival assay
  description: Construct a dnaJ deletion mutant in P. putida KT2440 and assay growth
    and viability after heat shock and hyperosmotic stress, alongside dnaK and grpE
    mutants, to test the requirement of the J-domain co-chaperone for stress tolerance
    and proteostasis.
- experiment_type: In vitro ATPase stimulation and refolding assay
  description: Purify recombinant P. putida DnaJ, DnaK, and GrpE and measure DnaJ-dependent
    stimulation of DnaK ATPase activity and reactivation of a heat-denatured model
    substrate (e.g. luciferase or malate dehydrogenase), including J-domain HPD-motif
    point mutants to confirm the mechanism.
- experiment_type: Zinc-center mutagenesis and functional assay
  description: Mutate the cysteine residues of zinc center 1 versus zinc center 2 and
    assay the effects on autonomous chaperone (anti-aggregation) activity versus DnaK
    interaction, to dissect the distinct roles of the two zinc sites in P. putida DnaJ.