esterosome

GO:0033117 · Membrane organelle · Membrane bounded organelle · Proposed

A vesicle filled with crystalline protein that shows sequence similarities with various esterases. [GO:0033117]

Has part: esterosome lumen (GO:0034467); esterosome membrane (GO:0033118)

Xrefs: uniprot.location:SL-0109 — Esterosome

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
esterosome membrane	Lipid	part of	`GO:0033118`			ESSENTIAL	Rough-endoplasmic-reticulum-like lipid bilayer that encloses the esterosome crystal-filled lumen. `GO:0033118` GO:0033118 defines the esterosome membrane as the lipid bilayer surrounding an esterosome. `DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 used electron microscopy to show that Dictyostelium discoideum esterosome crystals are enclosed by a membrane with rough endoplasmic reticulum characteristics.
esterosome crystal proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	cryS, D2		UNKNOWN	Major esterase-like proteins that pack into the crystalline core of the Dictyostelium esterosome. `DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 purified two major proteins from isolated Dictyostelium crystal fractions and localized antibodies against the crystal protein and the D2 protein to intracellular crystals.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

esterosome crystal proteins

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P21837`	Crystal protein	cryS	Dictyostelium discoideum (`NCBITaxon:44689`)	REVIEWED
Role and evidence (2 references) Reviewed UniProtKB entry for the Dictyostelium crystal protein encoded by cryS. `https://www.uniprot.org/uniprotkb/P21837` UniProtKB reviewed entry P21837 establishes the crystal protein accession, label and cryS gene identity. `DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 sequenced the Dictyostelium crystal protein N-terminus and localized the protein to esterosome crystals by immunoelectron microscopy.
`UniProtKB:P18142`	cAMP-regulated D2 protein	D2	Dictyostelium discoideum (`NCBITaxon:44689`)	REVIEWED
Role and evidence (2 references) Reviewed UniProtKB entry for the Dictyostelium cAMP-regulated D2 protein. `https://www.uniprot.org/uniprotkb/P18142` UniProtKB reviewed entry P18142 establishes the cAMP-regulated D2 protein accession, label and D2 gene identity. `DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 identified the 56 kDa esterosome crystal-associated protein as the D2-gene product.

Taxonomic distribution

NCBITaxon:44689 Dictyostelium discoideum — COMMON: Esterosomes were characterized in Dictyostelium discoideum aggregating cells as membrane-enclosed crystals with crystal and D2 protein cargo. [DOI:10.1083/jcb.110.3.669]

Canonical examples

NCBITaxon:44689 Dictyostelium discoideum — Social amoeba model in which esterosome crystals, their RER-like bounding membrane, and their crystal and D2 protein constituents were characterized. [DOI:10.1083/jcb.110.3.669]

Mechanism graphs

Esterase-like proteins pack into a membrane-bound crystal (ASSEMBLY)

In Dictyostelium discoideum, esterase-like crystal and D2 proteins accumulate in crystalline inclusion bodies that are enclosed by an RER-like esterosome membrane.

Subject	Predicate	Object	Evidence
esterosome crystal proteins	crystallize in	esterosome lumen	`DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 purified the crystal fraction and localized the crystal protein and the D2 protein to the crystals.
esterosome membrane	bounds	esterosome lumen	`GO:0034467` GO:0034467 defines the esterosome lumen as the volume enclosed by the esterosome membrane. `DOI:10.1083/jcb.110.3.669` Bomblies et al. 1990 showed that the crystals are membrane-enclosed.
esterosome membrane	is part of	esterosome	`GO:0033118` GO:0033118 defines the esterosome membrane as the lipid bilayer surrounding an esterosome.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the Dictyostelium esterosome crystal protein and cAMP-regulated D2 protein. This first esterosome record curates the verified proteins as members of the crystalline cargo while leaving exact family identifiers open. Both proteins match type-B carboxylesterase/lipase signatures, but the verified InterPro and Pfam accessions are broader than the esterosome-localized crystal proteins.

Evidence

GO:0033117 Gene Ontology cellular-component term for esterosome.
GO:0034467 Gene Ontology cellular-component term for the esterosome lumen.
GO:0033118 Gene Ontology cellular-component term for the esterosome membrane.
GO:0031410 Gene Ontology cellular-component parent term for cytoplasmic vesicle; UniProt also places the esterosome under its cytoplasmic vesicle location.
uniprot.location:SL-0109 — Esterosome UniProt Subcellular Location entry SL-0109 maps Esterosome to GO:0033117.
uniprot.location:SL-0108 — Esterosome membrane UniProt Subcellular Location entry SL-0108 maps Esterosome membrane to GO:0033118 and names it part of the esterosome.
uniprot.location:SL-0328 — Esterosome lumen UniProt Subcellular Location entry SL-0328 maps Esterosome lumen to GO:0034467 and names it part of the esterosome.
DOI:10.1083/jcb.110.3.669 Bomblies et al. 1990 described membrane-enclosed Dictyostelium discoideum esterosome crystals and characterized the crystal protein plus D2 protein as major crystal-associated constituents.

Curation history

2026-09-12T16:19:59Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T16:20:39Z codex · EXPANDED_RECORD — Added GO and UniProt Subcellular Location xrefs, esterosome membrane and lumen parts, RER-like membrane and reviewed-label-only crystal protein components, Dictyostelium scope and example curation, record-level DOI evidence, a nonmechanistic protein-crystal enclosure graph, and a grounding TODO for exact esterosome crystal protein families.
2026-09-12T16:21:06Z codex · REFINED_RECORD — Modeled the esterosome membrane graph edge as parthood rather than whole-organelle enclosure and narrowed the SL-0108 evidence note to the direct UniProt location-to-GO mapping.
2026-09-12T16:26:08Z codex · ADDRESS_REVIEW — Resolved #674 by removing membrane-location SL-0108 evidence from the esterosome crystal-protein component; resolved #675 by narrowing the Dictyostelium taxonomic-scope note to the directly characterized aggregation-stage crystals.

Source: data/structures/membrane_organelle/esterosome.yaml