mitochondrial envelope

GO:0005740 · Membrane organelle · Membrane · Proposed

The double lipid bilayer enclosing the mitochondrion and separating its contents from the cell cytoplasm; includes the intermembrane space. [GO:0005740]

Part of: mitochondrion (GO:0005739)

Has part: mitochondrial outer membrane (GO:0005741); mitochondrial inner membrane (GO:0005743); mitochondrial intermembrane space (GO:0005758); mitochondrial outer membrane translocase complex (GO:0005742)

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

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
mitochondrial outer membrane	Lipid	part of	`GO:0005741`	UNKNOWN	Cytoplasm-facing lipid bilayer of the mitochondrial envelope. `GO:0005741` GO:0005741 defines the mitochondrial outer membrane as the cytoplasm-facing lipid bilayer of the mitochondrial envelope.
mitochondrial inner membrane	Lipid	part of	`GO:0005743`	UNKNOWN	Lumen-facing lipid bilayer of the envelope that folds into cristae. `GO:0005743` GO:0005743 defines the mitochondrial inner membrane as the folded lumen-facing lipid bilayer of the mitochondrial envelope.
mitochondrial outer membrane translocase complex	Protein complex	part of	`GO:0005742`	UNKNOWN	Outer-membrane translocase that mediates entry of nuclear-encoded mitochondrial precursor proteins. `GO:0005742` GO:0005742 defines the TOM complex as a large mitochondrial outer membrane complex that mediates transport of proteins into mitochondrial compartments. `DOI:10.1016/j.cell.2009.08.005` Chacinska et al. 2009 review mitochondrial protein import through TOM and downstream sorting machineries.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — VARIABLE: Canonical mitochondrial envelopes occur with canonical mitochondria in eukaryotes, while some anaerobic lineages carry reduced mitochondrion-related organelles instead. [GO:0005739]
NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast mitochondria include outer- and inner-membrane proteomes with protein-import and oxidative-phosphorylation machinery. [DOI:10.1073/pnas.2135385100]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast mitochondria were purified to inventory matrix, outer-membrane, and inner-membrane mitochondrial proteins. [DOI:10.1073/pnas.2135385100]

Functions

protein import into mitochondrial matrix GO:0030150 — The mitochondrial envelope routes cytosolic precursor proteins through TOM and downstream inner-membrane machinery into the matrix.
- GO:0030150 GO:0030150 defines matrix protein import as import from the cytosol via TOM-TIM23-PAM.
- DOI:10.1016/j.cell.2009.08.005 Chacinska et al. 2009 review TOM entry and downstream TIM/PAM mitochondrial protein-import pathways.
oxidative phosphorylation GO:0006119 — Inner-envelope respiratory-chain activity contributes to membrane-gradient formation and ATP synthesis.
- GO:0006119 GO:0006119 defines oxidative phosphorylation as ATP formation coupled to respiratory-chain oxidation and membrane-gradient formation.
- DOI:10.1073/pnas.2135385100 Sickmann et al. 2003 recovered known oxidative phosphorylation machinery from purified budding-yeast mitochondria.

Mechanism graphs

Mitochondrial envelope routes matrix import (FUNCTION)

In budding yeast, the mitochondrial outer and inner membranes enclose the intermembrane space, while TOM at the outer membrane initiates precursor import into the matrix.

Subject	Predicate	Object	Evidence
mitochondrial envelope	encloses	mitochondrion	`GO:0005740` GO:0005740 defines the mitochondrial envelope as the double lipid bilayer enclosing the mitochondrion.
mitochondrial outer membrane	is part of	mitochondrial envelope	`GO:0005741` GO:0005741 defines the mitochondrial outer membrane as part of the mitochondrial envelope.
mitochondrial inner membrane	is part of	mitochondrial envelope	`GO:0005743` GO:0005743 defines the mitochondrial inner membrane as part of the mitochondrial envelope.
mitochondrial envelope	contains	mitochondrial intermembrane space	`GO:0005758` GO:0005758 defines the intermembrane space as the region between the inner and outer lipid bilayers of the mitochondrial envelope.
mitochondrial outer membrane translocase complex	spans	mitochondrial outer membrane	`GO:0005742` GO:0005742 places the TOM complex in the mitochondrial outer membrane.
mitochondrial outer membrane translocase complex	provides entry for	protein import into mitochondrial matrix	`DOI:10.1016/j.cell.2009.08.005` Chacinska et al. 2009 review TOM entry and downstream TIM23-PAM presequence import into the mitochondrial matrix.
mitochondrial inner membrane	supports	oxidative phosphorylation	`DOI:10.1073/pnas.2135385100` Sickmann et al. 2003 recovered oxidative-phosphorylation complexes in the purified budding-yeast mitochondrial proteome.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral records or component boundaries for TIM23, TIM22, SAM, MIA, respiratory-chain, and ATP synthase subcomplexes of the mitochondrial envelope. This first mitochondrial envelope record grounds the inner and outer membranes, the intermembrane space, and TOM exactly while avoiding broad, ungrounded aggregate classes for every import and respiratory subcomplex embedded in the envelope.

Evidence

GO:0005740 Gene Ontology cellular-component term for mitochondrial envelope.
GO:0031967 Gene Ontology cellular-component term for organelle envelope.
GO:0005739 Gene Ontology cellular-component term for mitochondrion.
GO:0005741 Gene Ontology cellular-component term for mitochondrial outer membrane.
GO:0005743 Gene Ontology cellular-component term for mitochondrial inner membrane.
GO:0005758 Gene Ontology cellular-component term for mitochondrial intermembrane space.
GO:0005742 Gene Ontology cellular-component term for the mitochondrial outer membrane translocase complex.
GO:0030150 Gene Ontology biological-process term for protein import into the mitochondrial matrix.
GO:0006119 Gene Ontology biological-process term for oxidative phosphorylation.
DOI:10.1073/pnas.2135385100 Sickmann et al. 2003, 'The proteome of Saccharomyces cerevisiae mitochondria', Proceedings of the National Academy of Sciences.
DOI:10.1016/j.cell.2009.08.005 Chacinska et al. 2009, 'Importing Mitochondrial Proteins: Machineries and Mechanisms', Cell.

Curation history

2026-09-12T05:48:32Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T05:49:15Z codex · EXPANDED_RECORD — Added organelle-envelope parentage, mitochondrion parthood, exact inner and outer membrane, intermembrane-space, and TOM parts, Eukaryota and Saccharomyces scope, import and oxidative-phosphorylation functions, DOI/GO evidence, a nonmechanistic envelope import graph, and a subcomplex-boundary grounding TODO.
2026-09-12T05:56:30Z codex · REVIEW_FIXES — Resolved PR #593 review issues #594 and #595 by downgrading unsupported inner- and outer-membrane essentiality assertions to UNKNOWN and adding the mitochondrion node plus GO:0005740 envelope topology edge to the graph.
2026-09-20T21:55:39Z codex · ADDRESSED_REVIEW — Retyped the TOM complex graph node from GENE_OR_PROTEIN to STRUCTURE.

Source: data/structures/membrane_organelle/mitochondrial_envelope.yaml