monolayer-surrounded lipid storage body outer lipid monolayer

GO:0034430 · Inclusion · Membrane · Proposed

The single layer of phospholipids surrounding a lipid storage body. [GO:0034430]

Synonyms: lipid storage body surface lipid monolayer; oil body outer lipid monolayer; oleosome outer lipid monolayer; spherosome outer lipid monolayer; lipid droplet outer lipid monolayer

Part of: lipid droplet (GO:0005811)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
phospholipid	Lipid	part of	`CHEBI:16247`			ESSENTIAL	Phospholipid molecules that assemble into the single-leaflet surface surrounding the hydrophobic lipid-storage core. `GO:0034430` GO:0034430 defines this structure as a single phospholipid layer surrounding a lipid storage body. `DOI:10.1007/s00018-015-1903-5` Wang 2015 reviews budding-yeast lipid droplets as neutral-lipid organelles bounded by a phospholipid monolayer.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast lipid droplets have a phospholipid monolayer surface around a neutral-lipid storage core. [DOI:10.1007/s00018-015-1903-5]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding yeast species used to define lipid-droplet phospholipid monolayers and neutral-lipid storage architecture. [DOI:10.1016/j.bbalip.2011.07.015]

Functions

lipid-droplet surface compartmentalization — The lipid-storage-body outer monolayer separates the hydrophobic storage-lipid core from the cytosol while exposing a surface for lipid-droplet proteins.
- GO:0005811 The GO lipid-droplet definition describes coalesced lipids surrounded by a phospholipid monolayer that may include associated proteins.
- PMID:29397034 Graef 2018 reviews budding-yeast lipid droplets as neutral-lipid storage organelles with a phospholipid monolayer surface.

Mechanism graphs

Phospholipids form the lipid-droplet outer monolayer (ASSEMBLY)

Phospholipids assemble into a single outer leaflet that is part of the lipid droplet and surrounds its hydrophobic storage-lipid core.

Subject	Predicate	Object	Evidence
phospholipid	assemble into	monolayer-surrounded lipid storage body outer lipid monolayer	`GO:0034430` The GO definition identifies the outer lipid monolayer as a single layer of phospholipids surrounding the lipid storage body.
monolayer-surrounded lipid storage body outer lipid monolayer	is part of	lipid droplet	`GO:0005811` The GO lipid-droplet definition describes a coalesced-lipid matrix surrounded by a phospholipid monolayer.
monolayer-surrounded lipid storage body outer lipid monolayer	surrounds	neutral lipid core	`PMID:29397034` Graef 2018 reviews budding-yeast lipid droplets as neutral-lipid stores bounded by a phospholipid monolayer.

Discussions

INTERPRETATION (RESOLVED): Should lipid-droplet surface proteins be curated as components of the outer lipid monolayer record? GO:0034430 denotes the lipid monolayer surrounding a lipid storage body. Proteins associated with that surface can be curated on the lipid-droplet record or as exact complexes after grounding, but this record's component list is limited to the phospholipids that form the monolayer itself.
CURATION_TODO (OPEN): Resolve oil-body, oleosome, spherosome, and plastoglobule monolayer boundaries before broadening this record beyond budding-yeast lipid droplets. This first pass imports GO synonymy for the generic lipid-storage-body outer monolayer but only curates Saccharomyces cerevisiae evidence. Plant/algal oil bodies, oleosomes, spherosomes, and the plastoglobule half-unit membrane need a separate boundary review before adding broader taxonomic rows or plastoglobule-specific component claims.

Evidence

GO:0034430 Gene Ontology cellular-component term for the outer lipid monolayer of a monolayer-surrounded lipid storage body.
GO:0005811 Gene Ontology cellular-component term for the containing lipid droplet.
DOI:10.1007/s00018-015-1903-5 Wang 2015 reviewed lipid-droplet dynamics in budding yeast.
PMID:29397034 Graef 2018 reviewed lipid-droplet-mediated lipid and protein homeostasis in budding yeast.
DOI:10.1016/j.bbalip.2011.07.015 Grillitsch et al. 2011 characterized the lipidome and proteome of Saccharomyces cerevisiae lipid particles/droplets.

Curation history

2026-09-16T00:25:24Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-16T00:26:14Z codex · EXPANDED_RECORD — Added GO synonymy, lipid-droplet parthood, a ChEBI-grounded phospholipid component, Saccharomyces scope, DOI and PMID evidence, a nonmechanistic outer-monolayer topology graph, and a resolved protein-boundary discussion.
2026-09-16T00:26:50Z codex · POLISH_RECORD — Aligned the ChEBI-grounded phospholipid component label with CHEBI:16247 and removed redundant record-level ChEBI evidence.
2026-09-16T00:32:37Z codex · FIX_VALIDATION — Retargeted the lipid-droplet surface-protein boundary discussion to the surface_phospholipids component anchor.
2026-09-16T00:38:37Z codex · ADDRESS_REVIEW — Resolved #1043 by adding an open TODO for oil-body, oleosome, spherosome, and plastoglobule lipid-monolayer boundary curation.

Source: data/structures/inclusion/monolayer_surrounded_lipid_storage_body_outer_lipid_monolayer.yaml