plastid outer membrane

GO:0009527 · Membrane organelle · Membrane · Proposed

The outer, i.e. cytoplasm-facing, lipid bilayer of the plastid envelope. [GO:0009527]

Synonyms: Outer plastidic membrane; Outer plastid membrane; Plastidic outer membrane

Part of: plastid envelope (GO:0009526)

Xrefs: uniprot.location:SL-0214 — Plastid outer membrane

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
plastid outer lipid bilayer	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)			ESSENTIAL	Cytoplasm-facing lipid bilayer that forms the outer boundary of the plastid envelope. `GO:0009527` GO:0009527 defines plastid outer membrane as the cytoplasm-facing lipid bilayer of the plastid envelope. `uniprot.location:SL-0214` — Plastid outer membrane UniProt SL-0214 identifies plastid outer membrane as the membrane facing the cytoplasm.

NCBITaxon:33090 Viridiplantae — COMMON: Green algae and land plants carry primary plastids bounded by double envelopes with cytoplasm-facing outer plastid membranes. [DOI:10.1098/rstb.2009.0103]
NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: The Chlamydomonas reinhardtii chloroplast outer membrane forms the cytosolic side of the chloroplast envelope and carries the Toc side of the TOC-TIC protein-import supercomplex. [DOI:10.1016/j.cell.2022.10.030]

NCBITaxon:3055 Chlamydomonas reinhardtii — Green-algal model used for structural analysis of a TOC-TIC supercomplex spanning the chloroplast outer and inner envelope membranes. [DOI:10.1016/j.cell.2022.10.030]

The plastid outer membrane is the cytoplasm-facing lipid bilayer of the plastid envelope and bounds the plastid intermembrane space.

Subject	Predicate	Object	Evidence
plastid outer membrane	is part of	plastid envelope	`GO:0009527` GO:0009527 defines this outer membrane as a lipid bilayer of the plastid envelope. `uniprot.location:SL-0214` — Plastid outer membrane UniProt SL-0214 identifies this structure as the outer membrane of a plastid.
plastid outer membrane	faces	cytoplasm	`GO:0009527` GO:0009527 identifies this plastid-envelope bilayer by its cytoplasm-facing orientation. `uniprot.location:SL-0214` — Plastid outer membrane UniProt SL-0214 describes the plastid outer membrane as facing the cytoplasm.
plastid outer membrane	bounds	plastid intermembrane space	`GO:0009529` GO:0009529 defines the plastid intermembrane space as the region between the inner and outer plastid envelope lipid bilayers.

CURATION_TODO (OPEN): Resolve an exact source-neutral grounding for the lipid constituent of the plastid outer membrane. The record is exactly grounded to GO:0009527 and UniProt SL-0214, but the lipid bilayer constituent is intentionally left as a reviewed-label-only component until an exact source-neutral lipid or membrane-constituent CURIE is curated.

GO:0009527 Gene Ontology cellular-component term for plastid outer membrane.
GO:0042170 Gene Ontology cellular-component term for generic plastid membranes.
GO:0009526 Gene Ontology cellular-component term for plastid envelope.
GO:0009529 Gene Ontology cellular-component term for plastid intermembrane space.
GO:0005737 — cytoplasm Gene Ontology cellular-component term for cytoplasm.
uniprot.location:SL-0214 — Plastid outer membrane UniProt Subcellular Location entry SL-0214 maps Plastid outer membrane to GO:0009527.
DOI:10.1098/rstb.2009.0103 Keeling 2010, The endosymbiotic origin, diversification and fate of plastids, Philosophical Transactions of the Royal Society B.
DOI:10.1016/j.cell.2022.10.030 Jin et al. 2022, Structure of a TOC-TIC supercomplex spanning two chloroplast envelope membranes, Cell.

2026-09-13T21:13:08Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T21:13:54Z codex · EXPANDED_RECORD — Added plastid-membrane parentage, plastid-envelope parthood, the UniProt SL-0214 xref and exact synonyms, a reviewed-label-only outer lipid bilayer component, Viridiplantae/Chlamydomonas scope, GO/UniProt/DOI evidence, a nonmechanistic topology graph, and a lipid-bilayer grounding TODO.