Bet v 1 (isoform Bet v 1-A / Bet v 1.0101), the major birch pollen allergen and the prototype of the pathogenesis-related protein 10 (PR-10 / Bet v 1) family. It has the START-like Bet v 1 fold with a large hydrophobic cavity that promiscuously binds plant secondary metabolites (sterols, flavonoids, cytokinins, fatty acids), and is proposed to act as a general plant lipophilic-ligand/steroid carrier and a defence (PR) protein. It is the dominant sensitizer in birch pollinosis and the basis of the PR-10 birch–food cross-reactivity syndrome. Its precise in-planta ligand and physiological role remain unresolved.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004864 protein phosphatase inhibitor activity | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: This activity is propagated from the structurally related PYR/PYL/RCAR abscisic acid receptors, which share the START/Bet v 1 fold and inhibit PP2C phosphatases. It is not established for Bet v 1, a PR-10 pollen protein, and reflects fold-based over-propagation. Reason: Fold-based over-propagation from PYR/PYL ABA receptors; not demonstrated for Bet v 1. |
| GO:0005634 nucleus | IEA GO_REF:0000118 | MARK AS OVER ANNOTATED | Summary: Nuclear localization is part of the ABA-receptor-like over-propagation; Bet v 1 is a cytoplasmic PR-10 protein. Reason: Over-propagated with the ABA-receptor annotations; inconsistent with the cytoplasmic localization of Bet v 1. |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: Bet v 1 is a cytoplasmic (and pollen-cytosolic) PR-10 protein. Reason: Consistent with the curated cytoplasmic localization. Supporting Evidence: file:BETPN/Betv1/Betv1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. |
| GO:0006952 defense response | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: As a pathogenesis-related (PR-10) protein, Bet v 1 is associated with plant defence responses. Reason: Plausible PR-10 family role; electronic and not specifically demonstrated for this protein. |
| GO:0009738 abscisic acid-activated signaling pathway | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: Propagated from PYR/PYL ABA receptors that share the Bet v 1 fold; not an established function of the PR-10 allergen. Reason: Fold-based over-propagation from ABA receptors; not demonstrated for Bet v 1. |
| GO:0010427 abscisic acid binding | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: The Bet v 1 cavity binds many lipophilic ligands; specific abscisic-acid binding is propagated from PYR/PYL ABA receptors and is not established for Bet v 1. Reason: Fold-based over-propagation; Bet v 1's documented binding is promiscuous (sterols/flavonoids/cytokinins), not specifically ABA as a receptor. |
| GO:0038023 signaling receptor activity | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: Receptor activity is propagated from the PYR/PYL ABA receptors; Bet v 1 is a ligand-carrier/PR protein, not a signalling receptor. Reason: Fold-based over-propagation from ABA receptors; not demonstrated for Bet v 1. |
| GO:0005496 steroid binding | IEA file:BETPN/Betv1/Betv1-uniprot.txt | NEW | Summary: NEW (proposed). UniProt notes Bet v 1 "may be a general steroid carrier protein"; its hydrophobic cavity binds sterols (and other plant lipophilic ligands). Steroid binding captures the best-supported molecular function and is not in GOA. Reason: Curated "general steroid carrier" function and the PR-10 ligand-binding cavity support a steroid/lipophilic-ligand binding molecular function. Supporting Evidence: file:BETPN/Betv1/Betv1-uniprot.txt May be a general steroid carrier protein. |
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Download this section (compressed HTML)Q: What is the physiological ligand of Bet v 1 in birch pollen, and is its function defence, hormone/sterol transport, or both?
Experiment: Identify endogenous ligands co-purifying with Bet v 1 from birch pollen by LC-MS, and test PP2C inhibition / ABA binding directly to confirm or exclude ABA-receptor activity.
Hypothesis: Bet v 1 functions as a plant lipophilic-ligand (sterol/flavonoid) carrier rather than an ABA receptor.
Type: ligand identification / biochemical assay
Bet v 1, major birch pollen allergen; PR-10 (Bet v 1 fold) promiscuous lipophilic-ligand carrier. MARK_AS_OVER_ANNOTATED the ABA-receptor cluster (PP inhibitor activity, ABA binding, ABA signaling, signaling receptor activity, nucleus) - fold-based over-propagation from PYR/PYL ABA receptors. ACCEPT cytoplasm; KEEP_AS_NON_CORE defense response; NEW steroid binding (general steroid carrier). Function gap: true in-planta ligand/role unresolved.
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