Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005576 extracellular region	IEA GO_REF:0000044	ACCEPT	Summary: Equ c 2 is a secreted dander lipocalin; extracellular localization is appropriate. Reason: Secretory lipocalin acting in the extracellular space. Supporting Evidence: file:HORSE/Equc2/Equc2-uniprot.txt SUBCELLULAR LOCATION: Secreted

Core Functions

Secreted dander lipocalin (calyx fold) of the horse, expected by family analogy to bind a small hydrophobic ligand in its beta-barrel calyx; the specific molecular function, endogenous ligand and physiological role are not established. Unlike its paralog Equ c 1, Equ c 2 carries no phylogenetic (IBA) odorant-binding annotation, so a specific molecular-function term is not asserted here.

Cellular Locations:

extracellular region

References

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

file:HORSE/Equc2/Equc2-uniprot.txt

UniProt entry P81216 (Dander allergen Equ c 2.0101), Equus caballus

Equ c 2 is a secreted horse dander lipocalin (calycin superfamily) allergen.

"Belongs to the calycin superfamily. Lipocalin family."

Suggested Experiments

Experiment: Identify co-purifying ligands of native Equ c 2 by LC-MS and test candidate ligands against recombinant protein by fluorescent-probe displacement.

Hypothesis: Equ c 2 binds a specific small hydrophobic ligand in its lipocalin calyx.

Type: ligand identification / biophysical binding assay

📚 Additional Documentation

Notes

(Equc2-notes.md)

Equc2 — curation notes (ALLERGENS backlog, mammalian inhalant cohort)

Equ c 2, horse dander lipocalin; only extracellular region in GOA; added NEW small molecule binding (lipocalin ligand, generic); ligand unknown -> function gap.

📄 View Raw YAML

id: P81216
gene_symbol: Equc2
product_type: PROTEIN
status: DRAFT
taxon:
  id: NCBITaxon:9796
  label: Equus caballus
description: >-
  Equ c 2 (isoform 2.0101), a secreted horse dander lipocalin (calycin superfamily,
  lipocalin family) and allergen. As a secretory lipocalin it is expected to bind a
  small hydrophobic ligand in its beta-barrel calyx, but the specific endogenous
  ligand and physiological role are not established (the protein was characterized
  largely at the protein-sequence/allergen level).
existing_annotations:
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Equ c 2 is a secreted dander lipocalin; extracellular localization is appropriate.
    action: ACCEPT
    reason: Secretory lipocalin acting in the extracellular space.
    supported_by:
    - reference_id: file:HORSE/Equc2/Equc2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Secreted'
core_functions:
- description: >-
    Secreted dander lipocalin (calyx fold) of the horse, expected by family analogy
    to bind a small hydrophobic ligand in its beta-barrel calyx; the specific
    molecular function, endogenous ligand and physiological role are not established.
    Unlike its paralog Equ c 1, Equ c 2 carries no phylogenetic (IBA) odorant-binding
    annotation, so a specific molecular-function term is not asserted here.
  locations:
  - id: GO:0005576
    label: extracellular region
  knowledge_gaps:
  - gap_statement: The specific molecular function and ligand bound by Equ c 2, and its endogenous physiological role, are undetermined.
    boundary: 'Established: Equ c 2 is a secreted lipocalin (calyx fold). Unknown: its specific molecular function, hydrophobic ligand and biological role.'
    gap_kind:
    - BIOLOGY
    provenance:
    - reference_id: file:HORSE/Equc2/Equc2-uniprot.txt
      supporting_text: Belongs to the calycin superfamily. Lipocalin family.
proposed_new_terms: []
suggested_questions:
- question: What ligand does Equ c 2 carry, and does it belong functionally with the odorant-binding or another lipocalin subgroup?
  experts: []
suggested_experiments:
- hypothesis: Equ c 2 binds a specific small hydrophobic ligand in its lipocalin calyx.
  description: Identify co-purifying ligands of native Equ c 2 by LC-MS and test candidate ligands against recombinant protein by fluorescent-probe displacement.
  experiment_type: ligand identification / biophysical binding assay
references:
- 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: file:HORSE/Equc2/Equc2-uniprot.txt
  title: UniProt entry P81216 (Dander allergen Equ c 2.0101), Equus caballus
  findings:
  - statement: Equ c 2 is a secreted horse dander lipocalin (calycin superfamily) allergen.
    supporting_text: Belongs to the calycin superfamily. Lipocalin family.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Curated UniProt record; supports secreted lipocalin classification. Specific ligand/role recorded as a knowledge gap.

Equc2

Gene Description