mitosome envelope

cellstructuremech:mitosome_envelope · Membrane organelle · Membrane · Proposed

The mitosomal envelope comprises the inner and outer mitosomal membrane including the intermembrane space. [uniprot.location:SL-0438 — Mitosome envelope]

Synonyms: mitosomal envelope

Part of: mitosome (GO:0032047)

Has part: mitosome inner membrane (cellstructuremech:mitosome_inner_membrane); mitosome outer membrane (cellstructuremech:mitosome_outer_membrane); mitosome intermembrane space (cellstructuremech:mitosome_intermembrane_space)

Xrefs: uniprot.location:SL-0438 — Mitosome envelope

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
mitosome outer membrane	Lipid	part of	`cellstructuremech:mitosome_outer_membrane`			UNKNOWN	Cytoplasm-facing lipid bilayer of the mitosome envelope. `uniprot.location:SL-0443` — Mitosome outer membrane UniProt SL-0443 identifies the mitosome outer membrane as the mitosomal membrane facing the cytoplasm.
mitosome inner membrane	Lipid	part of	`cellstructuremech:mitosome_inner_membrane`			UNKNOWN	Matrix-facing lipid bilayer that separates the mitosomal matrix from the intermembrane space. `uniprot.location:SL-0439` — Mitosome inner membrane UniProt Subcellular Location SL-0439 identifies the mitosome inner membrane as separating the mitosomal matrix from the intermembrane space.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — RARE: Mitosome envelopes occur patchily in anaerobic or microaerophilic microbial eukaryotes that retain highly reduced double-membrane mitochondrion-related organelles. [DOI:10.1111/jeu.12922]
NCBITaxon:5759 Entamoeba histolytica — COMMON: The Entamoeba mitochondrion-related mitosome was identified as a double-membrane organelle. [DOI:10.1046/j.1365-2958.1999.01414.x]

Canonical examples

NCBITaxon:5759 Entamoeba histolytica — Amoebozoan parasite in which mitosomes were initially described as mitochondrion-related double-membrane organelles. [DOI:10.1046/j.1365-2958.1999.01414.x]

Functions

mitosome compartmentalization — The mitosome envelope surrounds the reduced organelle and separates the matrix from the cytosol.
- uniprot.location:SL-0438 — Mitosome envelope UniProt SL-0438 defines the mitosome envelope as the inner and outer mitosomal membranes plus intermembrane space.
- DOI:10.1046/j.1365-2958.1999.01414.x Tovar et al. 1999 identified a double-membrane mitochondrion-related mitosome in Entamoeba histolytica.
mitosomal protein import boundary — The mitosome envelope is the double-membrane boundary crossed by nuclear-encoded, N-terminally targeted mitosomal proteins.
- DOI:10.1073/pnas.0500349102 Dolezal et al. 2005 tested Giardia mitosomal protein targeting and compared the import mode with hydrogenosomes.
- DOI:10.1038/nature01945 Tovar et al. 2003 localized nuclear-encoded ISC proteins to Giardia mitosomes.

Mechanism graphs

Mitosome envelope encloses the reduced organelle (FUNCTION)

The mitosome envelope contains inner and outer membranes plus the intermembrane space and surrounds the mitosome.

Subject	Predicate	Object	Evidence
mitosome envelope	encloses	mitosome	`uniprot.location:SL-0438` — Mitosome envelope UniProt SL-0438 identifies the inner and outer mitosomal membranes and intermembrane space as the mitosome envelope.
mitosome outer membrane	is part of	mitosome envelope	`uniprot.location:SL-0443` — Mitosome outer membrane UniProt SL-0443 defines the mitosome outer membrane as the membrane facing the cytoplasm.
mitosome inner membrane	is part of	mitosome envelope	`uniprot.location:SL-0439` — Mitosome inner membrane UniProt SL-0439 defines the mitosome inner membrane by its position between the matrix and intermembrane space.
mitosome envelope	contains	mitosome intermembrane space	`uniprot.location:SL-0440` — Mitosome intermembrane space UniProt SL-0440 defines the mitosome intermembrane space as the space between the inner and outer mitosomal membranes.

Discussions

CURATION_TODO (RESOLVED): Resolve an exact source-neutral record for the mitosome intermembrane space. UniProt provides an exact SL identifier for the remaining intermembrane-space child compartment, but no exact GO or CellStructureMech record was curated here for that location.

Evidence

uniprot.location:SL-0438 — Mitosome envelope UniProt Subcellular Location entry SL-0438 identifies the mitosome envelope, lists mitosomal envelope as an exact synonym, and places the envelope under the mitosome location.
uniprot.location:SL-0439 — Mitosome inner membrane UniProt Subcellular Location entry SL-0439 identifies the mitosome inner membrane as a child of the mitosome membrane.
uniprot.location:SL-0440 — Mitosome intermembrane space UniProt Subcellular Location entry SL-0440 identifies the mitosome intermembrane space as the space between inner and outer mitosomal membranes.
uniprot.location:SL-0443 — Mitosome outer membrane UniProt Subcellular Location entry SL-0443 identifies the mitosome outer membrane as a child of the mitosome membrane.
GO:0031967 Gene Ontology cellular-component parent term for organelle envelope.
GO:0032047 Gene Ontology cellular-component term for the containing mitosome.
DOI:10.1046/j.1365-2958.1999.01414.x Tovar et al. 1999, The mitosome, a novel organelle related to mitochondria in the amitochondrial parasite Entamoeba histolytica, Molecular Microbiology.
DOI:10.1038/nature01945 Tovar et al. 2003, Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation, Nature.
DOI:10.1073/pnas.0500349102 Dolezal et al. 2005, Giardia mitosomes and trichomonad hydrogenosomes share a common mode of protein targeting, Proceedings of the National Academy of Sciences.
DOI:10.1111/jeu.12922 Tachezy 2022, Hydrogenosomes and mitosomes: Mitochondria of anaerobic eukaryotes, Journal of Eukaryotic Microbiology.

Curation history

2026-09-13T19:08:21Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T19:09:20Z codex · EXPANDED_RECORD — Added the UniProt SL mitosomal-envelope synonym and xref, organelle-envelope parentage, mitosome parthood, reviewed-label-only inner and outer membrane lipid-bilayer components, rare anaerobic eukaryote and Entamoeba scope, compartmentalization and protein-import-boundary functions, GO/UniProt/DOI evidence, a nonmechanistic envelope topology graph, and a child-record grounding TODO.
2026-09-13T19:24:51Z codex · ADDRESSED_CURATION_TODO — Replaced the reviewed-label-only mitosome inner membrane component with a has_part link to cellstructuremech:mitosome_inner_membrane, grounded the topology graph inner-membrane node to the new exact record, and narrowed the child-record grounding TODO to the outer membrane and intermembrane space.
2026-09-13T19:40:58Z codex · ADDRESSED_CURATION_TODO — Replaced the reviewed-label-only mitosome outer membrane component with a has_part link to cellstructuremech:mitosome_outer_membrane, grounded the topology graph outer-membrane node to the new exact record, and narrowed the child-record grounding TODO to the intermembrane space.
2026-09-13T19:59:51Z codex · ADDRESSED_CURATION_TODO — Added cellstructuremech:mitosome_intermembrane_space as the remaining mitosome envelope has_part child, grounded the topology graph intermembrane-space node to the new exact record, and resolved the child-record grounding TODO.

Source: data/structures/membrane_organelle/mitosome_envelope.yaml