Equc4

UniProt ID: P82615
Organism: Equus caballus
Review Status: DRAFT
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Gene Description

Equ c 4 / latherin, a secreted horse protein of the BPI/LBP/PLUNC superfamily (PLUNC family) and a horse allergen. It is the major protein of horse sweat (and saliva), a highly surface-active biosurfactant that lowers surface tension to make the water-repellent coat wettable, promoting sweat spreading and evaporative cooling (thermoregulation). It is the prototype of the latherin/PLUNC family that also includes cat Fel d 8.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0043129 surfactant homeostasis
IBA
GO_REF:0000033 		ACCEPT
Summary: Latherin is a biosurfactant; surfactant homeostasis is consistent with its family and direct characterization.
Reason: Supported by phylogeny and the experimentally demonstrated surfactant function.
Supporting Evidence:
file:HORSE/Equc4/Equc4-uniprot.txt
Major protein in sweat, has surfactant properties. Has a role
GO:0005576 extracellular region
IEA
GO_REF:0000044 		ACCEPT
Summary: Latherin is secreted into sweat/saliva; extracellular localization is correct.
Reason: Consistent with secretion into sweat and saliva.
Supporting Evidence:
file:HORSE/Equc4/Equc4-uniprot.txt
Major protein in sweat, has surfactant properties. Has a role
GO:0008289 lipid binding
IEA
GO_REF:0000002 		ACCEPT
Summary: BPI/LBP/PLUNC-superfamily proteins bind lipids; lipid binding is consistent with latherin's surfactant fold.
Reason: Consistent with the lipid-binding PLUNC fold and surfactant activity.
Supporting Evidence:
file:HORSE/Equc4/Equc4-uniprot.txt
Belongs to the BPI/LBP/Plunc superfamily. Plunc family.
GO:0001659 temperature homeostasis
IDA
PMID:3753435
Isolation and characterization of latherin, a surface-active... 		ACCEPT
Summary: Latherin's surfactant activity wets the water-repellent coat and promotes sweat spreading/evaporation, contributing directly to evaporative cooling and temperature regulation.
Reason: Experimentally supported role in thermoregulation via sweat surfactant activity.
Supporting Evidence:
file:HORSE/Equc4/Equc4-uniprot.txt
Major protein in sweat, has surfactant properties. Has a role
GO:0043129 surfactant homeostasis
IDA
PMID:3753435
Isolation and characterization of latherin, a surface-active... 		ACCEPT
Summary: Direct (IDA) demonstration of latherin's surfactant function in sweat.
Reason: Experimentally demonstrated surfactant activity.
Supporting Evidence:
file:HORSE/Equc4/Equc4-uniprot.txt
Major protein in sweat, has surfactant properties. Has a role

Core Functions

Secreted biosurfactant (latherin/PLUNC family) that lowers surface tension to wet the hydrophobic coat, promoting sweat spreading and evaporative cooling; binds lipids consistent with the PLUNC fold.

Molecular Function:
lipid binding
Directly Involved In:
surfactant homeostasis temperature homeostasis
Cellular Locations:
extracellular region
Supporting Evidence:
  • file:HORSE/Equc4/Equc4-uniprot.txt
    Major protein in sweat, has surfactant properties. Has a role

References

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Suggested Questions for Experts

Q: How does latherin's PLUNC fold achieve its exceptional surface activity, and does Fel d 8 share the mechanism?

Suggested Experiments

Experiment: Compare surface-tension reduction (pendant drop) and lipid binding of recombinant latherin and Fel d 8.

Hypothesis: Equ c 4 / latherin reduces surface tension via a PLUNC-family lipid/air-water interface mechanism shared with Fel d 8.

Type: biophysical / surfactant assay

📚 Additional Documentation

Notes

(Equc4-notes.md)

Equc4 — curation notes (ALLERGENS backlog, mammalian inhalant cohort)

Equ c 4 = latherin; BPI/LBP/PLUNC surfactant of horse sweat (prototype of the Fel d 8 family); ACCEPT surfactant homeostasis (IBA/IDA), lipid binding, temperature homeostasis (IDA PMID:3753435), extracellular.

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