SSA2

id: P10592
gene_symbol: SSA2
product_type: PROTEIN
status: IN_PROGRESS
taxon:
  id: NCBITaxon:559292
  label: Saccharomyces cerevisiae
description: >-
  SSA2 encodes a constitutively expressed cytoplasmic Hsp70 chaperone in S. cerevisiae,
  highly homologous to SSA1 (97% amino acid identity). SSA2 is one of four SSA family
  members (SSA1-4) and is the most abundant, with approximately 364,000 molecules/cell
  (PMID:14562106), even more than SSA1. SSA2 functions as an ATP-dependent molecular
  chaperone that assists protein folding and refolding, interacts with Hsp90 and J-domain
  co-chaperones, participates in ubiquitin-dependent protein degradation, tRNA nuclear
  import, and is part of the HAP1 transcriptional repressor complex. SSA2 also binds
  human histatin 5 (HTN3) and mediates its fungicidal activity (PMID:12761219). SSA2 is
  found in the cytoplasm, cytosol, nucleus, plasma membrane, cell wall, vacuole membrane,
  mitochondria, and extracellular vesicles.
existing_annotations:
# ============================================================
# IBA ANNOTATIONS (phylogenetically inferred)
# ============================================================
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 nuclear localization is supported by NAS evidence from PMID:15102838 (HAP1
      repressor complex). As a close paralog of SSA1 (97% identity), SSA2 is expected to
      share nuclear localization. SSA1 has direct IDA evidence for nuclear localization
      (PMID:10347213).
    action: ACCEPT
    reason: >-
      Phylogenetically consistent. SSA2 is part of the HAP1 repressor complex in the
      nucleus (ComplexPortal CPX-1883). As a near-identical paralog of SSA1, nuclear
      localization is well-supported.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 is a major cytoplasmic Hsp70. IBA is consistent with IDA evidence from
      PMID:8755907 and UniProt subcellular location annotation.
    action: ACCEPT
    reason: >-
      Core localization. SSA2 is constitutively expressed and highly abundant in the
      cytoplasm.
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 has been detected at the plasma membrane by HDA (PMID:16622836). IBA is
      consistent.
    action: ACCEPT
    reason: >-
      Supported by proteomics data. SSA2, like SSA1, is associated with the plasma
      membrane.
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 has ATPase activity supported by ISS evidence from PMID:8151709. As a 97%
      identical paralog of SSA1, which has well-characterized ATPase activity (PMID:7737974),
      SSA2's ATPase activity is certain.
    action: ACCEPT
    reason: >-
      Core molecular function. The ATPase activity drives the chaperone cycle. SSA2 is
      97% identical to SSA1 whose ATPase activity is biochemically established.
- term:
    id: GO:0031072
    label: heat shock protein binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 interacts with numerous heat shock proteins including HSP82, HSC82, SSE1,
      SIS1, STI1, SBA1, and HSP26/HSP42. UniProt lists extensive IntAct interaction data.
    action: ACCEPT
    reason: >-
      Well-supported by extensive IPI data. SSA2 physically interacts with HSP82 (4
      experiments), HSC82 (3 experiments), SSE1 (4 experiments), SIS1 (5 experiments),
      STI1 (4 experiments), and other chaperones.
- term:
    id: GO:0044183
    label: protein folding chaperone
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 is a bona fide protein folding chaperone. PMID:8947547 demonstrated that
      immunodepletion of Ssa1/2p from yeast cytosol dramatically reduced refolding of
      denatured luciferase. PMID:9789005 showed SSA-dependent folding of newly translated
      OTC in vivo.
    action: ACCEPT
    reason: >-
      Core molecular function. SSA2 is an ATP-dependent protein folding chaperone,
      functionally interchangeable with SSA1 for refolding activity.
    supported_by:
      - reference_id: PMID:8947547
        supporting_text: "Depletion of Ssa1/2p had no effect on the ability of the yeast lysate to synthesize enzymatically active luciferase, but had a dramatic effect on the ability of the lysate to refold chemically denatured luciferase."
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 is primarily a cytosolic protein. IBA is consistent with IDA evidence from
      PMID:16806052.
    action: ACCEPT
    reason: >-
      Core localization. SSA2 is the major cytosolic Hsp70 along with SSA1.
- term:
    id: GO:0042026
    label: protein refolding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >-
      SSA2 is directly involved in protein refolding. PMID:8947547 demonstrated that
      Ssa1/2p depletion dramatically reduced refolding capacity of yeast cytosol.
    action: ACCEPT
    reason: >-
      Well-supported core function. Refolding of denatured proteins is a central activity
      of SSA2 as demonstrated by PMID:8947547.
    supported_by:
      - reference_id: PMID:8947547
        supporting_text: "These results demonstrate, for the first time, the refolding activity of Ssa1/2p in the context of the yeast cytosol, and define refolding activity as a chaperone function specific to Ssa1/2p"
# ============================================================
# IEA ANNOTATIONS (computationally inferred)
# ============================================================
- term:
    id: GO:0000049
    label: tRNA binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      IEA annotation for tRNA binding. Consistent with IDA evidence from PMID:25853343
      which demonstrated that SSA2 directly binds tRNA as part of a tRNA nuclear import
      system.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct but non-core. Supported by direct experimental evidence (IDA from
      PMID:25853343). tRNA binding is a specialized moonlighting activity of SSA2.
- term:
    id: GO:0000166
    label: nucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >-
      SSA2 binds ATP and ADP as part of its chaperone cycle. This is a parent term of ATP
      binding and is correct but overly general.
    action: ACCEPT
    reason: >-
      Correct but general. More specific terms (ATP binding, ATP hydrolysis activity) are
      also annotated, so this broader IEA is acceptable as a redundant parent.
- term:
    id: GO:0000329
    label: fungal-type vacuole membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 localization to the vacuole membrane is supported by IDA evidence from
      PMID:10745074, which showed cytosolic Hsp70 involvement in aminopeptidase I
      transport to the vacuole.
    action: ACCEPT
    reason: >-
      Correct. Consistent with direct experimental evidence (IDA from PMID:10745074).
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >-
      SSA2 binds ATP through its nucleotide-binding domain. This is core to its function.
      Also supported by IDA from PMID:10893257.
    action: ACCEPT
    reason: >-
      Correct and fundamental. ATP binding is essential for the SSA2 chaperone cycle.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >-
      Duplicate of the IBA and IDA annotations for cytoplasm. Correct.
    action: ACCEPT
    reason: >-
      Correct. Redundant with IBA and IDA annotations but acceptable.
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 is directly involved in protein folding as demonstrated experimentally
      (IDA from PMID:7867784, IMP from PMID:9448096). IEA is consistent.
    action: ACCEPT
    reason: >-
      Correct. Consistent with direct experimental evidence.
- term:
    id: GO:0006616
    label: SRP-dependent cotranslational protein targeting to membrane, translocation
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 has been implicated in protein translocation to the ER membrane (IMP from
      PMID:8754838). However, PMID:8947547 found that depletion of Ssa1/2p had no effect
      on translocation efficiency in vitro. The role may be more indirect.
    action: KEEP_AS_NON_CORE
    reason: >-
      Consistent with the existing IMP annotation from PMID:8754838, but this is not a
      core function. PMID:8947547 showed depletion had no effect on translocation
      efficiency in vitro, suggesting an indirect role.
    supported_by:
      - reference_id: PMID:8947547
        supporting_text: "Depletion of Ssa1/2p had no effect on the efficiency of translocation in this in vitro assay."
- term:
    id: GO:0009277
    label: fungal-type cell wall
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 has been detected in the cell wall by IDA (PMID:8755907). IEA is consistent.
      UniProt also annotates SSA2 to the cell wall.
    action: ACCEPT
    reason: >-
      Correct. Consistent with direct experimental evidence and UniProt annotation.
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >-
      Duplicate of IBA and ISS annotations. Correct InterPro-based annotation.
    action: ACCEPT
    reason: >-
      Correct. Redundant with IBA and ISS annotations but acceptable.
- term:
    id: GO:0033554
    label: cellular response to stress
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 is a heat shock protein involved in stress response. Although SSA2 is
      constitutively expressed (unlike the stress-induced SSA3/SSA4), it participates in
      protein quality control during stress.
    action: ACCEPT
    reason: >-
      Correct but general. SSA2 responds to and helps manage various stresses through its
      chaperone activity.
- term:
    id: GO:0043161
    label: proteasome-mediated ubiquitin-dependent protein catabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 participates in ubiquitin-dependent protein degradation. Consistent with IGI
      evidence from PMID:27178214.
    action: KEEP_AS_NON_CORE
    reason: >-
      Correct but non-core. SSA2 assists in presenting misfolded substrates to the
      ubiquitin-proteasome system as part of its broader protein quality control role.
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      GO:0051082 (unfolded protein binding) is being considered for obsoletion. SSA2 does
      bind unfolded proteins, but this is part of its chaperone activity, not a standalone
      binding function. The appropriate replacement is GO:0140662 (ATP-dependent protein
      folding chaperone).
    action: MODIFY
    reason: >-
      GO:0051082 is targeted for obsoletion. SSA2 binds unfolded proteins as part of its
      ATP-dependent chaperone cycle. The correct annotation is GO:0140662 (ATP-dependent
      protein folding chaperone) or the already-present GO:0044183 (protein folding
      chaperone).
    proposed_replacement_terms:
      - id: GO:0140662
        label: ATP-dependent protein folding chaperone
- term:
    id: GO:0051170
    label: import into nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: >-
      SSA2 is involved in tRNA import into the nucleus (IMP from PMID:25853343,
      PMID:33074312). This IEA is a broader parent term consistent with the experimental
      evidence.
    action: ACCEPT
    reason: >-
      Correct but general. Consistent with the more specific experimental annotation for
      tRNA import into nucleus.
# ============================================================
# PROTEIN BINDING IPI ANNOTATIONS
# ============================================================
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:14729968
  review:
    summary: >-
      IPI evidence from ctf13-30/CTF13 haploinsufficiency screen. SSA2 is a chaperone
      that binds many client proteins.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone that by definition binds many
      proteins. Better captured by GO:0044183 (protein folding chaperone).
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:15766533
  review:
    summary: >-
      IPI evidence for SSA2 binding HSP82 and HSC82 from chaperone network mapping.
      These are well-known Hsp70-Hsp90 interactions.
    action: MODIFY
    reason: >-
      Protein binding is uninformative. The Hsp70-Hsp90 interaction is better captured
      by GO:0031072 (heat shock protein binding) which is already annotated via IBA.
    proposed_replacement_terms:
      - id: GO:0031072
        label: heat shock protein binding
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16284124
  review:
    summary: >-
      IPI evidence for SSA2 binding proteasome subunits from a proteasome interactome
      study.
    action: MODIFY
    reason: >-
      Protein binding is uninformative. The SSA2-proteasome interaction relates to its
      role in ubiquitin-dependent protein degradation.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16429126
  review:
    summary: >-
      Large-scale proteome survey (Gavin et al. 2006) identifying many SSA2 interaction
      partners by TAP-MS.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone. The interactions represent
      chaperone-client and chaperone-cochaperone relationships.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16606443
  review:
    summary: >-
      IPI evidence from analysis of WW domain-containing proteins and their interacting
      partners.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17441508
  review:
    summary: >-
      IPI evidence for SSA2 binding SGT2 via Ydj1 co-chaperone.
    action: MODIFY
    reason: >-
      Protein binding is uninformative. The interaction with SGT2/Ydj1 relates to SSA2's
      chaperone function.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17892321
  review:
    summary: >-
      Structure-templated predictions of protein interactions.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:19536198
  review:
    summary: >-
      Atlas of chaperone-protein interactions (Gong et al. 2009). Systematic mapping of
      SSA2 chaperone-client interactions.
    action: MODIFY
    reason: >-
      Protein binding is uninformative. These interactions represent chaperone-client
      relationships inherent to SSA2's chaperone function.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:37070168
  review:
    summary: >-
      RNA-dependent interactome study.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:37968396
  review:
    summary: >-
      Social and structural architecture of yeast protein interactome. Large-scale study.
    action: MODIFY
    reason: >-
      Protein binding is uninformative for a chaperone.
    proposed_replacement_terms:
      - id: GO:0044183
        label: protein folding chaperone
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:9819422
  review:
    summary: >-
      IPI evidence for SSA2 binding HSP82 and CPR7 via Cns1.
    action: MODIFY
    reason: >-
      Protein binding is uninformative. The Ssa2-Hsp82/Cpr7 interaction is a chaperone
      network interaction better captured by GO:0031072.
    proposed_replacement_terms:
      - id: GO:0031072
        label: heat shock protein binding
# ============================================================
# NAS ANNOTATIONS
# ============================================================
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: NAS
  original_reference_id: PMID:15102838
  review:
    summary: >-
      NAS annotation from ComplexPortal for SSA2 nuclear localization in context of the
      HAP1 repressor complex (CPX-1883). Consistent with IBA.
    action: ACCEPT
    reason: >-
      Correct. SSA2 is present in the nucleus as part of the HAP1 repressor complex.
- term:
    id: GO:0045892
    label: negative regulation of DNA-templated transcription
  evidence_type: NAS
  original_reference_id: PMID:15102838
  review:
    summary: >-
      SSA2 is part of the HAP1 transcriptional repressor complex (ComplexPortal CPX-1883)
      where it represses HAP1-dependent transcription in the absence of heme.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but secondary function. SSA2 acts as a repressive chaperone holdase for
      HAP1, preventing transcriptional activation. This is not a core molecular function
      but rather a consequence of its chaperone activity on a specific client.
- term:
    id: GO:0070482
    label: response to oxygen levels
  evidence_type: NAS
  original_reference_id: PMID:15102838
  review:
    summary: >-
      SSA2 is part of the HAP1 complex that responds to heme/oxygen levels.
    action: KEEP_AS_NON_CORE
    reason: >-
      Secondary consequence of SSA2's role in the HAP1 repressor complex, not a core
      function.
- term:
    id: GO:0070482
    label: response to oxygen levels
  evidence_type: NAS
  original_reference_id: PMID:9632766
  review:
    summary: >-
      Same process annotation from a different reference. PMID:9632766 describes the
      higher-order HAP1 complex mechanism.
    action: KEEP_AS_NON_CORE
    reason: >-
      Duplicate process annotation for the same indirect role. SSA2 participates in
      oxygen/heme signaling through the HAP1 complex but this is not its core function.
# ============================================================
# IDA/IMP/IGI/ISS/HDA ANNOTATIONS (experimental evidence)
# ============================================================
- term:
    id: GO:1903561
    label: extracellular vesicle
  evidence_type: IDA
  original_reference_id: PMID:38711329
  review:
    summary: >-
      PMID:38711329 detected SSA2 in extracellular vesicles during thermotolerance
      studies.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but peripheral localization. SSA2 in extracellular vesicles likely reflects
      its abundance rather than a specific targeting function.
- term:
    id: GO:0009267
    label: cellular response to starvation
  evidence_type: IMP
  original_reference_id: PMID:25853343
  review:
    summary: >-
      PMID:25853343 showed SSA2 involvement in tRNA nuclear import which is regulated by
      nutrient status/starvation.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but secondary function. The starvation response of SSA2 is related to its
      role in tRNA import regulation.
- term:
    id: GO:0035719
    label: tRNA import into nucleus
  evidence_type: IMP
  original_reference_id: PMID:33074312
  review:
    summary: >-
      PMID:33074312 demonstrated SSA2's role in tRNA nuclear import via mutant phenotype
      analysis.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but specialized function. tRNA nuclear import is a moonlighting activity
      of SSA2 distinct from its core chaperone function.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: HDA
  original_reference_id: PMID:24769239
  review:
    summary: >-
      HDA evidence from mitochondrial proteome/phosphoproteome study. SSA2 was detected
      in mitochondrial fractions.
    action: ACCEPT
    reason: >-
      Correct. SSA2 associates with mitochondria, consistent with IDA from PMID:16806052
      and its role in protein translocation across mitochondrial membranes.
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: HDA
  original_reference_id: PMID:16622836
  review:
    summary: >-
      HDA evidence from plasma membrane proteome study. SSA2 was detected in the plasma
      membrane fraction.
    action: ACCEPT
    reason: >-
      Correct. SSA2 is associated with the plasma membrane, consistent with IBA.
- term:
    id: GO:0043161
    label: proteasome-mediated ubiquitin-dependent protein catabolic process
  evidence_type: IGI
  original_reference_id: PMID:27178214
  review:
    summary: >-
      PMID:27178214 demonstrated SSA family requirement for ubiquitin-dependent
      degradation of short-lived and abnormal proteins via genetic interaction.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but secondary function. SSA2 assists in presenting misfolded substrates to
      the ubiquitin-proteasome system as part of its broader protein quality control role.
- term:
    id: GO:0000049
    label: tRNA binding
  evidence_type: IDA
  original_reference_id: PMID:25853343
  review:
    summary: >-
      PMID:25853343 demonstrated that cytosolic Hsp70 (SSA2) directly binds tRNA as part
      of a tRNA nuclear import system.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but specialized function. tRNA binding is a moonlighting activity of SSA2
      related to its role in tRNA nuclear import.
- term:
    id: GO:0035719
    label: tRNA import into nucleus
  evidence_type: IMP
  original_reference_id: PMID:25853343
  review:
    summary: >-
      PMID:25853343 demonstrated SSA2's role in tRNA import into the nucleus.
    action: KEEP_AS_NON_CORE
    reason: >-
      Genuine but specialized function. Same as the other tRNA import annotation, from
      a different PMID.
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: ISS
  original_reference_id: PMID:8151709
  review:
    summary: >-
      ISS annotation based on molecular evolution of the HSP70 multigene family.
      Consistent with SSA2's function as an ATPase.
    action: ACCEPT
    reason: >-
      Correct. SSA2 has ATPase activity essential for its chaperone cycle. Redundant with
      IBA but acceptable.
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: ISS
  original_reference_id: PMID:8151709
  review:
    summary: >-
      GO:0051082 is targeted for obsoletion. SSA2 binds unfolded proteins as part of its
      ATP-dependent chaperone cycle, not as a standalone binding activity.
    action: MODIFY
    reason: >-
      GO:0051082 is being obsoleted. The correct replacement is GO:0140662 (ATP-dependent
      protein folding chaperone). SSA2 binds unfolded proteins as part of its chaperone
      function.
    proposed_replacement_terms:
      - id: GO:0140662
        label: ATP-dependent protein folding chaperone
- term:
    id: GO:0000329
    label: fungal-type vacuole membrane
  evidence_type: IDA
  original_reference_id: PMID:10745074
  review:
    summary: >-
      PMID:10745074 showed cytosolic Hsp70s are involved in transport of aminopeptidase I
      from cytoplasm into the vacuole, and SSA2 localizes to the vacuole membrane.
    action: ACCEPT
    reason: >-
      Correct localization supported by direct experimental evidence.
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IDA
  original_reference_id: PMID:10893257
  review:
    summary: >-
      PMID:10893257 demonstrated that SSA2 binds ATP, and this binding is required for
      import of fructose-1,6-bisphosphatase into Vid vesicles.
    action: ACCEPT
    reason: >-
      Core molecular function with direct experimental evidence.
    supported_by:
      - reference_id: PMID:10893257
        supporting_text: "The heat shock protein Ssa2p was identified as one of the ATP binding proteins involved in FBPase import."
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:8755907
  review:
    summary: >-
      PMID:8755907 identified Hsp70 family members including SSA2 in the cell wall and
      confirmed cytoplasmic localization.
    action: ACCEPT
    reason: >-
      Correct core localization with direct experimental evidence.
- term:
    id: GO:0005739
    label: mitochondrion
  evidence_type: IDA
  original_reference_id: PMID:16806052
  review:
    summary: >-
      PMID:16806052 detected SSA2 in mitochondrial fractions. SSA2 likely associates with
      mitochondria in the context of protein import.
    action: ACCEPT
    reason: >-
      Correct. SSA2 associates with mitochondria, consistent with HDA from PMID:24769239
      and its role in maintaining precursors in import-competent conformations.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: PMID:16806052
  review:
    summary: >-
      PMID:16806052 confirmed SSA2 cytosolic localization.
    action: ACCEPT
    reason: >-
      Correct core localization. SSA2 is predominantly cytosolic.
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IDA
  original_reference_id: PMID:7867784
  review:
    summary: >-
      Direct assay demonstrating SSA2 involvement in protein folding.
    action: ACCEPT
    reason: >-
      Core biological process. Direct experimental demonstration of SSA2's role in protein
      folding.
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: IMP
  original_reference_id: PMID:9448096
  review:
    summary: >-
      PMID:9448096 showed that ssa1ssa2 mutants had significantly lower luciferase
      activity than wild type, demonstrating SSA proteins are needed for folding of
      proteins. The reduced folding capacity in ssa1ssa2 cells closely correlated with
      the amount of Ssa proteins present.
    action: ACCEPT
    reason: >-
      Core biological process. Mutant phenotype demonstrates SSA2 (with SSA1) is required
      for protein folding in vivo.
    supported_by:
      - reference_id: PMID:9448096
        supporting_text: "The luciferase activity was significantly lower in ssa1ssa2 transformants than in the wild type (wt) cell transformed with the same plasmid"
      - reference_id: PMID:9448096
        supporting_text: "It is suggested that constitutional Ssa \"chaperones\" are needed for the folding of proteins and, in cells lacking Ssa1 and Ssa2, the increased Ssa4 is thought to partly compensate for their role in the folding of luciferase in vivo"
- term:
    id: GO:0006616
    label: SRP-dependent cotranslational protein targeting to membrane, translocation
  evidence_type: IMP
  original_reference_id: PMID:8754838
  review:
    summary: >-
      PMID:8754838 showed that SSA-deficient mutants (ssa1ts ssa2 ssa3 ssa4) had
      translocation defects for prepro-alpha-factor and proteinase A. However,
      PMID:8947547 later showed depletion of Ssa1/2p had no effect on translocation
      efficiency in vitro.
    action: KEEP_AS_NON_CORE
    reason: >-
      The direct role in SRP-dependent translocation is debated. PMID:8947547 showed
      depletion did not affect translocation efficiency. The in vivo phenotype from
      PMID:8754838 may reflect SSA2's general chaperone function keeping precursors
      translocation-competent.
    supported_by:
      - reference_id: PMID:8754838
        supporting_text: "Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-alpha-factor and proteinase A was inhibited."
      - reference_id: PMID:8947547
        supporting_text: "Depletion of Ssa1/2p had no effect on the efficiency of translocation in this in vitro assay."
- term:
    id: GO:0009277
    label: fungal-type cell wall
  evidence_type: IDA
  original_reference_id: PMID:8755907
  review:
    summary: >-
      PMID:8755907 directly identified SSA2 as a cell wall protein. UniProt also
      annotates SSA2 subcellular location as "Secreted, cell wall."
    action: ACCEPT
    reason: >-
      Correct localization. SSA2 is present in the cell wall.
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IGI
  original_reference_id: PMID:9789005
  review:
    summary: >-
      PMID:9789005 showed that the SSA class of Hsp70 proteins assists folding of newly
      translated OTC in vivo. The IGI evidence comes from genetic interaction among SSA
      family members. GO:0051082 is targeted for obsoletion.
    action: MODIFY
    reason: >-
      GO:0051082 is being obsoleted. PMID:9789005 actually demonstrates chaperone
      activity, not mere binding. The correct replacement is GO:0140662 (ATP-dependent
      protein folding chaperone).
    proposed_replacement_terms:
      - id: GO:0140662
        label: ATP-dependent protein folding chaperone
    supported_by:
      - reference_id: PMID:9789005
        supporting_text: "yeast cytosolic OTC is assisted to its native state by the SSA class of yeast cytosolic Hsp70 proteins"
# ============================================================
# NEW ANNOTATIONS (suggested additions)
# ============================================================
- term:
    id: GO:0140662
    label: ATP-dependent protein folding chaperone
  evidence_type: IDA
  original_reference_id: PMID:8947547
  review:
    summary: >-
      SSA2 is an ATP-dependent protein folding chaperone. PMID:8947547 demonstrated that
      Ssa1/2p depletion dramatically reduced refolding of denatured luciferase in yeast
      cytosol, and PMID:9789005 showed SSA-dependent folding of newly translated OTC.
      GO:0140662 is the most specific and accurate MF term, replacing the obsoleting
      GO:0051082. UniProt already assigns this via InterPro (IEA).
    action: NEW
    reason: >-
      GO:0140662 (ATP-dependent protein folding chaperone) is the most specific and
      accurate molecular function term for SSA2. It replaces the obsoleting GO:0051082
      and is more specific than GO:0044183.
    additional_reference_ids:
      - PMID:9789005
      - PMID:9448096
    supported_by:
      - reference_id: PMID:8947547
        supporting_text: "These results demonstrate, for the first time, the refolding activity of Ssa1/2p in the context of the yeast cytosol"
      - reference_id: PMID:9789005
        supporting_text: "yeast cytosolic OTC is assisted to its native state by the SSA class of yeast cytosolic Hsp70 proteins"
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:7867784
  title: Cooperation of the molecular chaperone Ydj1 with specific Hsp70 homologs to
    suppress protein aggregation.
  findings:
    - statement: Ydj1 cooperated with Ssa Hsp70 proteins in the prevention of protein aggregation
      supporting_text: "Ydj1p cooperated with Ssa Hsp70 proteins in the prevention of protein aggregation, but not with the Ssb Hsp70 proteins."
- id: PMID:8151709
  title: Molecular evolution of the HSP70 multigene family.
  findings:
    - statement: ISS-based annotation of ATPase and unfolded protein binding for SSA2
      supporting_text: "The Saccharomyces cerevisiae HSP70 family is comprised of eight members"
- id: PMID:8754838
  title: Functional interaction of cytosolic hsp70 and a DnaJ-related protein, Ydj1p,
    in protein translocation in vivo.
  findings:
    - statement: SSA-deficient mutants show translocation defects for specific ER-targeted proteins
      supporting_text: "Of six proteins destined for the endoplasmic reticulum, the translocation of only prepro-alpha-factor and proteinase A was inhibited"
- id: PMID:8755907
  title: Members of the Hsp70 family of proteins in the cell wall of Saccharomyces cerevisiae.
  findings:
    - statement: Identified SSA2 in the cell wall and confirmed cytoplasmic localization
      supporting_text: "the heat shock protein 70 (Hsp70) products of these genes, previously thought to be restricted to the cell interior, are also present in the cell wall"
- id: PMID:8947547
  title: The refolding activity of the yeast heat shock proteins Ssa1 and Ssa2 defines
    their role in protein translocation.
  findings:
    - statement: Demonstrated Ssa1/2 refolding activity with denatured luciferase
    - statement: Found Ssa1/2 depletion does not affect translocation in vitro
- id: PMID:9448096
  title: Role of Hsp70 subfamily, Ssa, in protein folding in yeast cells, seen in
    luciferase-transformed ssa mutants.
  findings:
    - statement: Demonstrated SSA proteins are needed for protein folding in vivo
- id: PMID:9632766
  title: 'Molecular mechanism governing heme signaling in yeast: a higher-order complex
    mediates heme regulation of the transcriptional activator HAP1.'
  findings:
    - statement: Described the HAP1 higher-order complex mechanism with Hsp70
- id: PMID:9789005
  title: Folding in vivo of a newly translated yeast cytosolic enzyme is mediated by
    the SSA class of cytosolic yeast Hsp70 proteins.
  findings:
    - statement: SSA class Hsp70s assist de novo folding of newly translated cytosolic enzymes
- id: PMID:9819422
  title: Cns1 is an essential protein associated with the hsp90 chaperone complex in
    Saccharomyces cerevisiae that can restore cyclophilin 40-dependent functions in
    cpr7Delta cells.
  findings:
    - statement: SSA2 associates with the Hsp90 chaperone complex via Cns1/Cpr7
- id: PMID:10745074
  title: Cytosolic Hsp70s are involved in the transport of aminopeptidase 1 from the
    cytoplasm into the vacuole.
  findings:
    - statement: SSA2 involved in Ape1 transport to vacuole and localizes to vacuole membrane
- id: PMID:10893257
  title: The heat shock protein Ssa2p is required for import of fructose-1,6-bisphosphatase
    into Vid vesicles.
  findings:
    - statement: SSA2 binds ATP and is required for FBPase import into Vid vesicles
- id: PMID:14562106
  title: Global analysis of protein expression in yeast.
  findings:
    - statement: SSA2 present at 364,000 molecules/cell in log phase
- id: PMID:14729968
  title: The ctf13-30/CTF13 genomic haploinsufficiency modifier screen identifies the
    yeast chromatin remodeling complex RSC, which is required for the establishment of
    sister chromatid cohesion.
  findings: []
- id: PMID:15102838
  title: 'A novel mode of chaperone action: heme activation of Hap1 by enhanced association
    of Hsp90 with the repressed Hsp70-Hap1 complex.'
  findings:
    - statement: SSA2 is part of the HAP1 repressor complex (CPX-1883)
- id: PMID:15766533
  title: 'Navigating the chaperone network: an integrative map of physical and genetic
    interactions mediated by the hsp90 chaperone.'
  findings:
    - statement: Mapped SSA2 interactions with Hsp90 chaperone network
- id: PMID:16284124
  title: 'An integrated mass spectrometry-based proteomic approach: quantitative analysis
    of tandem affinity-purified in vivo cross-linked protein complexes (QTAX) to decipher
    the 26 S proteasome-interacting network.'
  findings:
    - statement: SSA2 interacts with the 26S proteasome
- id: PMID:16429126
  title: Proteome survey reveals modularity of the yeast cell machinery.
  findings:
    - statement: Large-scale TAP-MS identifying numerous SSA2 interactors
- id: PMID:16606443
  title: Comparative analysis of Saccharomyces cerevisiae WW domains and their interacting
    proteins.
  findings: []
- id: PMID:16622836
  title: The plasma membrane proteome of Saccharomyces cerevisiae and its response to
    the antifungal calcofluor.
  findings:
    - statement: SSA2 detected in the plasma membrane proteome
- id: PMID:16806052
  title: MMI1 (YKL056c, TMA19), the yeast orthologue of the translationally controlled
    tumor protein (TCTP) has apoptotic functions and interacts with both microtubules
    and mitochondria.
  findings:
    - statement: SSA2 detected in cytosol and mitochondrial fractions
- id: PMID:17441508
  title: SGT2 and MDY2 interact with molecular chaperone YDJ1 in Saccharomyces cerevisiae.
  findings:
    - statement: SSA2 interacts with SGT2 via Ydj1 co-chaperone
- id: PMID:17892321
  title: Structure-templated predictions of novel protein interactions from sequence
    information.
  findings: []
- id: PMID:19536198
  title: 'An atlas of chaperone-protein interactions in Saccharomyces cerevisiae: implications
    to protein folding pathways in the cell.'
  findings:
    - statement: Systematic mapping of SSA2 chaperone-client interactions
- id: PMID:24769239
  title: Quantitative variations of the mitochondrial proteome and phosphoproteome during
    fermentative and respiratory growth in Saccharomyces cerevisiae.
  findings:
    - statement: SSA2 detected in mitochondrial fraction
- id: PMID:25853343
  title: Cytosolic Hsp70 and co-chaperones constitute a novel system for tRNA import
    into the nucleus.
  findings:
    - statement: SSA2 binds tRNA and facilitates its import into the nucleus
- id: PMID:27178214
  title: The requirements of yeast Hsp70 of SSA family for the ubiquitin-dependent degradation
    of short-lived and abnormal proteins.
  findings:
    - statement: SSA family required for ubiquitin-dependent degradation
- id: PMID:33074312
  title: A novel assay provides insight into tRNAPhe retrograde nuclear import and re-export
    in S. cerevisiae.
  findings:
    - statement: SSA2 role in tRNA nuclear import
      supporting_text: "the Hsp70 protein Ssa2 mediates import specifically in the latter"
- id: PMID:37070168
  title: RNA-dependent interactome allows network-based assignment of RNA-binding protein
    function.
  findings: []
- id: PMID:37968396
  title: The social and structural architecture of the yeast protein interactome.
  findings: []
- id: PMID:38711329
  title: Thermotolerance in S. cerevisiae as a model to study extracellular vesicle
    biology.
  findings:
    - statement: SSA2 detected in extracellular vesicles
- id: PMID:12761219
  title: Candida albicans Ssa1/2p is the cell envelope binding protein for human salivary
    histatin 5.
  findings:
    - statement: SSA2 binds human histatin 5 and mediates its fungicidal activity
core_functions:
  - molecular_function:
      id: GO:0140662
      label: ATP-dependent protein folding chaperone
    directly_involved_in:
      - id: GO:0006457
        label: protein folding
      - id: GO:0042026
        label: protein refolding
    locations:
      - id: GO:0005829
        label: cytosol
    description: >-
      SSA2 is the most abundant cytoplasmic Hsp70 in S. cerevisiae (364,000 molecules/cell),
      functioning as an ATP-dependent protein folding chaperone. It is 97% identical to SSA1
      and functionally interchangeable for refolding of denatured proteins (PMID:8947547).
      SSA2 uses ATP hydrolysis cycles to assist both de novo folding of newly translated
      proteins (PMID:9789005) and refolding of stress-denatured proteins (PMID:8947547,
      PMID:9448096). It cooperates with J-domain co-chaperones (Ydj1, Sis1), nucleotide
      exchange factors (Sse1/Sse2, Fes1), and Hsp90 (HSP82/HSC82). SSA2 also has specialized
      roles in tRNA nuclear import (PMID:25853343), ubiquitin-dependent protein degradation
      (PMID:27178214), and transcriptional regulation via the HAP1 repressor complex
      (PMID:15102838).