family_id: PANTHER:PTHR11527 family_name: HEAT-SHOCK PROTEIN 20 FAMILY MEMBER preferred_name: Small heat-shock and alpha-crystallin proteins summary: Small heat-shock proteins and alpha-crystallins form oligomeric assemblies that interact with non-native proteins. Client recognition, oligomer structure, expression response and cellular localization vary among organisms and paralogs. functional_coherence: MOSTLY_COHERENT coherence_reason: The diatom target has the small-HSP domain, and biochemical small-HSP studies establish unfolded-client binding and oligomerization. Heat, salt and hydrogen-peroxide responses require the relevant organism and conditions. Holdase-mediated protection is not proof that the target independently refolds denatured clients. subfamilies: - label: Small heat-shock and alpha-crystallin proteins description: The diatom target has the small-HSP domain, and biochemical small-HSP studies establish unfolded-client binding and oligomerization. Heat, salt and hydrogen-peroxide responses require the relevant organism and conditions. Holdase-mediated protection is not proof that the target independently refolds denatured clients. representative_members: - id: UniProtKB:B7FXQ8 gene_symbol: B7FXQ8 organism: Phaeodactylum tricornutum (strain CCAP 1055/1) gene_review: genes/PHATC/B7FXQ8/B7FXQ8-ai-review.yaml term_assessments: - assessed_term: id: GO:0009651 label: response to salt stress scope: UNRESOLVED scope_reason: A small-HSP domain supports a proteostasis comparison, not a salt-response phenotype. The cited Hsp16.5 oligomer/client study does not assay diatom salinity response. Salt induction, protection or loss-of-function effects in the relevant organism are needed to resolve this process across family branches. supported_by: - reference_id: PMID:29983375 supporting_text: 'Small heat-shock proteins (sHSPs) are molecular chaperones that bind partially and globally unfolded states of their client proteins.' - reference_id: PMID:29983375 supporting_text: 'the archaeal Hsp16.5, which forms ordered and symmetric 24-subunit oligomers' - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR002068; A-crystallin/Hsp20_dom. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR008978; HSP20-like_chaperone. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR031107; Small_HSP. - assessed_term: id: GO:0051259 label: protein complex oligomerization scope: UNRESOLVED scope_reason: The Hsp16.5 study directly demonstrates 24-, 48- and engineered intermediate oligomeric assemblies, establishing oligomerization in characterized small HSPs. Their variable oligomeric states and specialized alpha-crystallin relatives prevent a fixed assembly stoichiometry or unconditional grant to every detected fragment. The complete assembly-competent set is unresolved. supported_by: - reference_id: PMID:29983375 supporting_text: 'Small heat-shock proteins (sHSPs) are molecular chaperones that bind partially and globally unfolded states of their client proteins.' - reference_id: PMID:29983375 supporting_text: 'the archaeal Hsp16.5, which forms ordered and symmetric 24-subunit oligomers' - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR002068; A-crystallin/Hsp20_dom. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR008978; HSP20-like_chaperone. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR031107; Small_HSP. - assessed_term: id: GO:0006457 label: protein folding scope: UNRESOLVED scope_reason: Binding unfolded clients and preventing aggregation can assist productive folding through a chaperone network, but neither proves autonomous refolding or an exact folding pathway for the diatom target. The cited work measures client binding and oligomer plasticity. It supports a holdase-related hypothesis while leaving the broad protein-folding process and its complete branch distribution unresolved. supported_by: - reference_id: PMID:29983375 supporting_text: They bind their client proteins in stable complexes thereby inhibiting aggregation - reference_id: PMID:29983375 supporting_text: 'Small heat-shock proteins (sHSPs) are molecular chaperones that bind partially and globally unfolded states of their client proteins.' - reference_id: PMID:29983375 supporting_text: 'the archaeal Hsp16.5, which forms ordered and symmetric 24-subunit oligomers' - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR002068; A-crystallin/Hsp20_dom. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR008978; HSP20-like_chaperone. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR031107; Small_HSP. - assessed_term: id: GO:0009408 label: response to heat scope: UNRESOLVED scope_reason: Heat response is common in small-HSP biology but must be established physiologically, especially for constitutive alpha-crystallins and lineage-specific proteins. The cited structural study does not test heat-induced expression or thermotolerance of the diatom protein. The family fold alone does not identify the heat-responsive branches. supported_by: - reference_id: PMID:29983375 supporting_text: 'Small heat-shock proteins (sHSPs) are molecular chaperones that bind partially and globally unfolded states of their client proteins.' - reference_id: PMID:29983375 supporting_text: 'the archaeal Hsp16.5, which forms ordered and symmetric 24-subunit oligomers' - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR002068; A-crystallin/Hsp20_dom. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR008978; HSP20-like_chaperone. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR031107; Small_HSP. - assessed_term: id: GO:0042542 label: response to hydrogen peroxide scope: UNRESOLVED scope_reason: Hydrogen-peroxide response is a stimulus-specific physiological claim distinct from generic client aggregation suppression. The cited oligomer/client experiment does not measure peroxide exposure or a peroxide-defense phenotype. The diatom target and the full family cannot receive this process from the small-HSP domain alone. supported_by: - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR002068; A-crystallin/Hsp20_dom. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR008978; HSP20-like_chaperone. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: DR InterPro; IPR031107; Small_HSP. - reference_id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt supporting_text: FT DOMAIN 47..155 references: - id: PMID:29983375 title: Engineering of a Polydisperse Small Heat-Shock Protein Reveals Conserved Motifs of Oligomer Plasticity. - id: file:genes/PHATC/B7FXQ8/B7FXQ8-uniprot.txt - id: file:interpro/panther/PTHR11527/PTHR11527-entries.csv - id: file:interpro/panther/PTHR11527/PTHR11527-paint.tsv review_status: COMPLETE reviewed_by: codex review_date: '2026-09-10' notes: 'PHATC/B7FXQ8: requested accession B7FXQ8; current record B7FXQ8; sequence length 163; source cohort ARGO50. Family boundaries were assessed using the fetched member set and the cited domain, literature and analytical evidence. Gene-review verdicts and ARBA assertions are not independent validation. PANTHER subfamily labels and membership are recorded from the frozen UniProt records and panther.obo; they do not by themselves prove functional uniformity within a subfamily. PAINT rows were inspected as ancestral assertions, but node placement is not adjudicated without the relevant descendant tree/alignment. No residue requirement is encoded without a verified sequence-version anchor. A target-level refutation is not a family-wide NOT_APPLICABLE judgment. Exact protein-name-only predictions are treated as family-identification hypotheses rather than invented GO predictions. The original B7FXQ8 ProtNLM output includes GO:0051082 (unfolded protein binding), which current QuickGO marks obsolete. Its biological binding hypothesis remains supported at the general small-HSP level by PMID:29983375. This paper demonstrates oligomer-dependent binding to destabilized clients and describes aggregation suppression; it does not establish the diatom target''s delivery to an acceptor or location required by the current GO:0140309 unfolded protein holdase activity definition. GO:0044183 protein folding chaperone instead requires assistance in folding the client. A specific current molecular-function replacement remains unresolved, so neither activity is granted merely from the old binding prediction. The original prediction is preserved unchanged in its source review.'