Serum albumin of the domestic cat, the allergen Fel d 2. The most abundant plasma protein and the archetypal multi-ligand transport protein of the ALB/AFP/VDB family: it binds and carries water, metal ions (zinc, calcium, magnesium, sodium, potassium), fatty acids, hormones, bilirubin and many drugs, and its principal physiological role is regulation of the colloidal osmotic pressure of blood. It is the major plasma zinc transporter and a major calcium/ magnesium transporter, and it sequesters the bacterial siderophore enterobactin, contributing to nutritional immunity. As an allergen, Fel d 2 is a minor, cross-reactive component responsible for cross-sensitization between mammalian albumins (e.g. pork-cat syndrome).
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0031667 response to nutrient levels | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Broad physiological-response term reflecting albumin's role in nutrient/metabolite transport and starvation responses. Reason: Generic process association; not a core, distinguishing function of albumin. |
| GO:1903981 enterobactin binding | IBA GO_REF:0000033 | ACCEPT | Summary: Albumin binds the bacterial siderophore enterobactin and inhibits enterobactin-mediated iron uptake by bacteria, a documented function. Reason: Supported by the curated UniProt function describing enterobactin binding. Supporting Evidence: file:FELCA/ALB/ALB-uniprot.txt enterobactin and inhibits enterobactin-mediated iron uptake of E.coli |
| GO:0005576 extracellular region | IEA GO_REF:0000120 | ACCEPT | Summary: Albumin is a secreted plasma protein; extracellular localization is correct and central. Reason: Albumin functions in blood plasma (extracellular region). |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Albumin is a secreted protein; any cytoplasmic signal reflects its biosynthetic route through the hepatocyte, not its functional compartment. Reason: Biosynthetic/transit localization; the functional compartment is extracellular plasma. |
| GO:0036094 small molecule binding | IEA GO_REF:0000118 | MARK AS OVER ANNOTATED | Summary: Generic parent term; albumin's specific ligand-binding activities (fatty acid, metal ion, enterobactin) are the informative annotations. Reason: Uninformative broad parent of the specific binding functions. |
| GO:0072562 blood microparticle | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Albumin is a common constituent of blood microparticles, consistent with its high plasma abundance. Reason: Plausible plasma-derived localization; not a distinguishing functional compartment. |
| GO:1903981 enterobactin binding | IEA GO_REF:0000118 | ACCEPT | Summary: Electronic duplicate of the enterobactin-binding function. Reason: Consistent with the curated enterobactin-binding/nutritional-immunity function. Supporting Evidence: file:FELCA/ALB/ALB-uniprot.txt enterobactin and inhibits enterobactin-mediated iron uptake of E.coli |
| GO:0051902 negative regulation of mitochondrial depolarization | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Similarity-transferred cytoprotective process; downstream/indirect for a plasma carrier protein. Reason: Indirect, similarity-based association; not a core albumin function. |
| GO:0072732 cellular response to calcium ion starvation | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Reflects albumin's role as a plasma calcium reservoir/transporter; broad process term. Reason: Similarity-based process association tied to calcium transport; non-core. |
| GO:1903981 enterobactin binding | ISS GO_REF:0000024 | ACCEPT | Summary: Similarity-transferred enterobactin binding, agreeing with the curated function. Reason: Consistent with documented enterobactin binding. Supporting Evidence: file:FELCA/ALB/ALB-uniprot.txt enterobactin and inhibits enterobactin-mediated iron uptake of E.coli |
| GO:0003677 DNA binding | ISS GO_REF:0000024 | MARK AS OVER ANNOTATED | Summary: Albumin is not a bona fide sequence-specific DNA-binding protein; any DNA association is non-specific and reflects its promiscuous, highly abundant ligand-binding surface rather than a genuine molecular function. Reason: Misleading functional assignment for a plasma carrier protein; likely an artifact of promiscuous binding propagated by similarity. |
| GO:0005504 fatty acid binding | ISS GO_REF:0000024 | ACCEPT | Summary: Fatty acid binding and transport is one of albumin's best-characterized, core molecular functions. Reason: Classic, well-established albumin function; central to its role as a plasma lipid carrier. Supporting Evidence: file:FELCA/ALB/ALB-uniprot.txt Binds water, Ca(2+), Na(+), K(+), fatty acids, hormones, |
| GO:0009267 cellular response to starvation | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Broad process term linked to albumin's role in nutrient/metabolite supply. Reason: Generic, similarity-based process; non-core. |
| GO:0015643 toxic substance binding | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Albumin binds and carries many drugs, toxins and metabolites; toxic-substance binding reflects this promiscuous carrier role. Reason: Real but secondary facet of albumin's general small-molecule carrier function. Supporting Evidence: file:FELCA/ALB/ALB-uniprot.txt bilirubin and drugs. Its main function is the regulation of the |
| GO:0019825 oxygen binding | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Similarity-transferred oxygen binding; a minor facet relative to albumin's principal ligand-carrier roles. Reason: Minor/secondary binding activity; non-core. |
| GO:0030170 pyridoxal phosphate binding | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Albumin binds pyridoxal 5'-phosphate (vitamin B6) in plasma; one of its many small-molecule ligands. Reason: Specific but secondary ligand-binding facet of the general carrier function. |
| GO:0032991 protein-containing complex | ISS GO_REF:0000024 | MARK AS OVER ANNOTATED | Summary: Uninformative, top-level cellular-component term. Reason: Generic root-level term carrying no specific information. |
Loading supporting content…
Download this section (compressed HTML)Q: Does cat serum albumin share the human albumin zinc/calcium "crosstalk" site (Asp-273 equivalent), and how does its metal-transport stoichiometry compare?
Experiment: Measure fatty-acid and Zn2+/Ca2+ binding of purified cat albumin by ITC and compare site occupancy to human serum albumin via competition assays and structural modeling.
Hypothesis: Fel d 2 (cat albumin) reproduces the canonical mammalian albumin fatty-acid and metal-ion binding profile.
Type: biophysical binding assay
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)