MIB complex
A mitochondrial intermembrane-space-spanning assembly that couples inner-membrane MICOS to outer-membrane SAM and includes a conserved DNAJC11-related protein and metaxin 1. [GO:0140275]
Synonyms: mitochondrial intermembrane space bridging complex; mitofilin complex
Part of: mitochondrial inner membrane (GO:0005743)
Has part: MICOS complex (GO:0061617); SAM complex (GO:0001401)
Components
| Component | Type | Part of / acts on | Grounding | Genes | Stoichiometry | Essential | Role |
|---|---|---|---|---|---|---|---|
| MICOS complex | Protein complex | part of | GO:0061617 | Inner-membrane subcomplex of the membrane-spanning assembly.
| |||
| SAM complex | Protein complex | part of | GO:0001401 | Outer-membrane subcomplex associated with MICOS.
|
Canonical examples
NCBITaxon:4896Schizosaccharomyces pombe — Cross-linked lysate IP/MS recovered SAM and a DNAJC11 homolog with MICOS. This is association evidence, not purified reconstitution or fixed stoichiometry. [DOI:10.1016/j.cub.2024.04.028]
Functions
- mitochondrial membrane bridging — Connects mitochondrial inner- and outer-membrane protein assemblies across the intermembrane space.
GO:0140275The GO definition specifies a bridging assembly spanning MICOS and SAM.DOI:10.1016/j.cub.2024.04.028The Introduction describes MIB as a trans-boundary MICOS-SAM assembly; Figure 1 supports association in fission yeast.
Mechanism graphs
MIB connects MICOS and SAM (FUNCTION)
Structural organization of the membrane bridge, not a temporal assembly pathway.
| Subject | Predicate | Object | Evidence |
|---|---|---|---|
| MICOS complex | is part of | MIB complex |
|
| SAM complex | is part of | MIB complex |
|
| MIB complex | mediates | mitochondrial membrane bridging |
|
Discussions
- INTERPRETATION (RESOLVED): Does MIB duplicate MICOS, SAM or MIMAS? MIB denotes the larger bridging assembly; its existing MICOS and SAM records denote subcomplexes. The GO synonym mitofilin complex is retained without treating every mitofilin-containing assembly as MIB.
- CURATION_TODO (OPEN): Resolve exact DNAJC11-related and metaxin family mappings and strain-matched protein examples. The two component rows describe subcomplexes, not an exhaustive protein inventory. Separate metaxin representation must not double-count a SAM constituent. No individual family or reference-strain accession is asserted before its scope is verified.
- INTERPRETATION (RESOLVED): Should Mmc1 be encoded as an obligatory MIB constituent? Mmc1 associates with MICOS, but the source separates its activity from MICOS assembly. Association alone does not establish an obligatory MIB subunit.
- CONTROVERSY (OPEN): Resolve differing mitofilin C-terminal truncation results before adding a domain-level yeast bridging mechanism. Two budding-yeast studies report opposite changes in SAM co-isolation after C-terminal truncation. The fission-yeast example does not resolve that experimental disagreement.
Evidence
GO:0140275Exact cellular-component identity, synonyms and composition boundary.GO:0098800Verified GO is-a parent of MIB.GO:0005743Containing inner mitochondrial membrane, not an identity mapping.DOI:10.1016/j.cub.2024.04.028Kumar et al. 2024, A dynamin superfamily-like pseudoenzyme coordinates with MICOS to promote cristae architecture. PMID 38692277; native PMC11187654.319 JATS checked against MD5 10930e607aec0699d936e157acfdacce.
Curation history
2026-10-04T21:05:04Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-10-04T21:07:34Zcodex · CURATED_RECORD — Added exact GO identity and subcomplexes, a fission-yeast association example, structural bridging function, nonmechanistic graph and bounded component/experimental uncertainties.