nuclear inner membrane

GO:0005637 · Membrane organelle · Membrane · Proposed

The inner, i.e. lumen-facing, lipid bilayer of the nuclear envelope. [GO:0005637]

Synonyms: inner nuclear membrane

Part of: nuclear envelope (GO:0005635)

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
nuclear inner membrane lipid bilayer	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)			ESSENTIAL	Lumen-facing lipid-bilayer constituent of the nuclear envelope inner membrane. `GO:0005637` GO:0005637 defines the nuclear inner membrane as the lumen-facing lipid bilayer of the nuclear envelope.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast integral inner nuclear membrane proteins Heh1p and Heh2p are targeted to the INM through a karyopherin-alpha/beta- and Ran-GTP-dependent pathway. [DOI:10.1038/nature05075]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast Heh1p and Heh2p model in which classical-NLS-like signals and karyopherins mediate integral inner nuclear membrane protein targeting. [DOI:10.1038/nature05075]

Functions

integral inner nuclear membrane protein targeting — Karyopherin-dependent targeting delivers integral Heh1p and Heh2p cargo to the yeast nuclear inner membrane.
- DOI:10.1038/nature05075 King et al. 2006 showed that karyopherin-alpha, karyopherin-beta1, the Ran GTPase cycle, and classical-NLS-like motifs are required for inner nuclear membrane targeting of integral proteins.

Mechanism graphs

Yeast inner nuclear membrane receives integral protein cargo (FUNCTION)

The nuclear inner membrane is the lumen-facing nuclear envelope membrane and receives integral Heh1p and Heh2p cargo through karyopherin-mediated targeting.

Subject	Predicate	Object	Evidence
nuclear inner membrane	is part of	nuclear envelope	`GO:0005637` GO:0005637 defines the nuclear inner membrane as the lumen-facing lipid bilayer of the nuclear envelope.
nuclear envelope lumen	lies between	nuclear inner membrane	`GO:0005641` GO:0005641 defines the nuclear envelope lumen as the region between the two nuclear envelope bilayers. `GO:0005637` GO:0005637 identifies the inner nuclear envelope bilayer.
nuclear envelope lumen	lies between	nuclear outer membrane	`GO:0005641` GO:0005641 defines the nuclear envelope lumen as the region between the two nuclear envelope bilayers. `GO:0005640` GO:0005640 identifies the outer nuclear envelope bilayer.
Kap60/Kap95 karyopherin system	mediates	integral inner nuclear membrane protein targeting	`DOI:10.1038/nature05075` King et al. 2006 found that karyopherin-alpha and karyopherin-beta1 are required for integral inner nuclear membrane protein targeting.
integral inner nuclear membrane protein targeting	targets	nuclear inner membrane	`DOI:10.1038/nature05075` King et al. 2006 found that a karyopherin-alpha/beta route targets integral protein cargo to the inner nuclear membrane.
Heh1p	localizes to	nuclear inner membrane	`DOI:10.1038/nature05075` King et al. 2006 described Heh1p as an integral inner nuclear membrane protein cargo.
Heh2p	localizes to	nuclear inner membrane	`DOI:10.1038/nature05075` King et al. 2006 described Heh2p as an integral inner nuclear membrane protein cargo.
Heh1p	is cargo of	integral inner nuclear membrane protein targeting	`DOI:10.1038/nature05075` King et al. 2006 used Heh1p as an integral inner nuclear membrane protein cargo in the karyopherin-dependent targeting assay.
Heh2p	is cargo of	integral inner nuclear membrane protein targeting	`DOI:10.1038/nature05075` King et al. 2006 also used Heh2p as an integral inner nuclear membrane protein cargo in the karyopherin-dependent targeting assay.

Discussions

INTERPRETATION (RESOLVED): Keep the paired nuclear outer membrane and nuclear envelope lumen as neighboring nuclear-envelope structures rather than as nuclear inner membrane components. GO:0005637 denotes the inner bilayer of the nuclear envelope, GO:0005640 denotes the distinct outer bilayer, and GO:0005641 denotes the lumen between those bilayers.
CURATION_TODO (OPEN): Resolve exact source-neutral groundings for Heh1p, Heh2p, Kap60, and Kap95. This record uses Heh1p, Heh2p, and the Kap60/Kap95 import system in the functional graph to capture the cited budding-yeast inner nuclear membrane example but leaves those proteins ungrounded until exact UniProtKB or family-level identifiers can be verified.

Evidence

GO:0005637 Gene Ontology cellular-component term for nuclear inner membrane.
GO:0031090 Gene Ontology cellular-component parent term for organelle membrane.
GO:0005635 Gene Ontology cellular-component term for the containing nuclear envelope.
GO:0005640 Gene Ontology cellular-component term for the paired nuclear outer membrane.
GO:0005641 Gene Ontology cellular-component term for the nuclear envelope lumen between the inner and outer nuclear membranes.
DOI:10.1038/nature05075 King et al. 2006, 'Karyopherin-mediated import of integral inner nuclear membrane proteins', Nature.

Curation history

2026-09-15T06:19:26Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-15T06:20:13Z codex · EXPANDED_RECORD — Added exact inner nuclear membrane synonymy, organelle-membrane parentage, nuclear-envelope parthood, a reviewed-label-only lipid-bilayer component, Saccharomyces Heh1p/Heh2p karyopherin-import evidence, a nonmechanistic inner-membrane protein-import graph, and boundary and protein-grounding discussions.
2026-09-15T06:21:05Z codex · REFINED_GRAPH — Connected Heh1p and Heh2p directly to the nuclear inner membrane node in the import graph.
2026-09-15T06:31:52Z codex · REVIEW_FIX — Addressed review issues #941 and #942 by narrowing the custom function to integral inner nuclear membrane protein targeting, adding an explicit targeting edge to the nuclear inner membrane, and modelling Heh1p and Heh2p as cargo of that process.

Source: data/structures/membrane_organelle/nuclear_inner_membrane.yaml