GO:0042719 mitochondrial intermembrane space chaperone complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0042719 describes the mitochondrial intermembrane space chaperone complex, also called the small TIM complex, a protein-containing complex located in the mitochondrial intermembrane space that chaperones hydrophobic proteins to the TIM22 complex for insertion into the inner membrane.
• The complex is built from small TIM proteins, principally TIM9, TIM10 and TIM12, which form hexameric TIM9-TIM10 and TIM9-TIM12 assemblies that shield substrates in the aqueous intermembrane space.
• Its best-characterized substrates are mitochondrial metabolite carriers and other multi-spanning inner membrane proteins, making the complex essential for mitochondrial biogenesis and cellular energy metabolism.
• Loss or dysfunction of small TIM proteins impairs mitochondrial protein import and has been linked to neurodegeneration, mitochondrial disease and cancer cell metabolism.
• The complex is regulated by proteostasis pathways, including the ubiquitin-proteasome system and cytosolic quality-control import routes, which control the abundance of intermembrane space proteins.
• Research on GO:0042719 uses biochemical reconstitution, crosslinking, proteomics and CRISPR-engineered cell models to define substrate handover and complex assembly.
Description
The mitochondrial intermembrane space chaperone complex (GO:0042719) is a conserved protein-containing complex that operates in the mitochondrial intermembrane space (IMS) to guide hydrophobic membrane proteins to the TIM22 insertase for integration into the mitochondrial inner membrane. The complex is widely known as the small TIM complex because its core subunits, TIM9, TIM10 and TIM12, are small zinc-binding proteins that assemble into hexameric chaperone particles. Because the IMS is an aqueous compartment, hydrophobic transmembrane segments of carrier proteins must be shielded during transit, and the small TIM chaperones provide this essential solubility and targeting function. The term is central to mitochondrial biogenesis research because defects in small TIM function block the import of metabolite carriers and other inner membrane proteins, thereby disrupting oxidative phosphorylation, metabolite exchange and mitochondrial dynamics. Small TIM proteins also participate in broader IMS proteostasis, cooperating with chaperones such as CLPB and small heat shock proteins to maintain the solubility of aggregation-prone IMS proteins. In addition, the abundance of IMS proteins is controlled by cytosolic and mitochondrial quality-control pathways, including the ubiquitin-proteasome system and the import of misfolded cytosolic proteins into mitochondria. For researchers, GO:0042719 provides a precise annotation for experiments that interrogate chaperone-substrate handover, inner membrane protein insertion and mitochondrial proteostasis. Understanding this complex helps explain how mitochondria maintain their proteome and why its failure contributes to human disease.
mitochondrial intermembrane space chaperone complex At A Glance
| GO ID | GO:0042719 |
|---|---|
| GO term | mitochondrial intermembrane space chaperone complex |
| Ontology | cellular_component |
| Synonym | mitochondrial intermembrane space protein transporter complex; small TIM complex |
| Major function | Chaperones hydrophobic proteins to the TIM22 complex for insertion into the mitochondrial inner membrane |
| Subunit composition | Small TIM proteins, principally TIM9, TIM10 and TIM12, forming hexameric TIM9-TIM10 and TIM9-TIM12 particles |
| Subcellular location | Mitochondrial intermembrane space, associated with the inner membrane and TIM22 insertase |
| Representative substrates | Mitochondrial metabolite carriers and other multi-spanning inner membrane proteins |
| Related quality-control pathways | Ubiquitin-proteasome system and cytosolic protein import into mitochondria |
What Is GO:0042719?
GO:0042719, mitochondrial intermembrane space chaperone complex, is a cellular component ontology term for a mitochondrial protein-containing complex that resides in the mitochondrial intermembrane space and chaperones proteins to the TIM22 complex for insertion into the mitochondrial inner membrane. Its synonym, small TIM complex, reflects the small size of its TIM9, TIM10 and TIM12 subunits, which form hexameric chaperone assemblies that bind hydrophobic carrier proteins and deliver them to the inner membrane insertase machinery.
Why Is mitochondrial intermembrane space chaperone complex Important in Cell Biology?
GO:0042719 is important because the small TIM chaperone complex is a gatekeeper for the biogenesis of mitochondrial inner membrane proteins, especially the metabolite carrier family that controls the exchange of ions, nucleotides and metabolic intermediates across the inner membrane. Without functional small TIM chaperones, hydrophobic carrier proteins aggregate or are mistargeted, leading to defective oxidative phosphorylation and mitochondrial dysfunction. The complex also interfaces with IMS proteostasis networks, including CLPB and small heat shock proteins, and with cytosolic quality-control pathways that regulate IMS protein abundance. These connections make GO:0042719 relevant to mitochondrial disease, neurodegeneration and cancer metabolism, and they provide a defined experimental target for CRISPR-based functional genomics.
• Defines the chaperone step that delivers hydrophobic carrier proteins to the TIM22 insertase for inner membrane integration.
• Essential for assembly of mitochondrial metabolite carriers and maintenance of oxidative phosphorylation.
• Prevents aggregation of hydrophobic IMS proteins by providing a shielded aqueous environment.
• Links mitochondrial protein import to IMS proteostasis through cooperation with CLPB and small heat shock proteins.
• Interfaces with the ubiquitin-proteasome system that regulates IMS protein turnover.
• Connects to cytosolic proteostasis through import of misfolded proteins into mitochondria.
• Provides a mechanistic explanation for mitochondrial dysfunction in carrier-protein-related disease.
• Serves as a target for biochemical reconstitution and structural studies of chaperone-substrate complexes.
• Enables CRISPR knockout and tagging strategies to test small TIM gene function in human cells.
• Supports biomarker and drug-target discovery in mitochondrial and metabolic disease research.
What Happens During mitochondrial intermembrane space chaperone complex?
Substrate recognition in the intermembrane space
In simple terms: The small TIM chaperones grab hydrophobic carrier proteins as soon as they enter the intermembrane space so they do not clump together.
Hydrophobic inner membrane proteins, particularly metabolite carriers, are translocated across the outer membrane through the TOM complex and emerge into the intermembrane space, where the small TIM chaperone complex binds them. The hexameric TIM9-TIM10 particle provides a chaperone surface that recognizes hydrophobic segments and keeps substrates soluble in the aqueous IMS. This recognition step is the first committed event of the GO:0042719 pathway and prevents off-pathway aggregation.
Chaperone-substrate handover to TIM22
In simple terms: The chaperones hand the carrier protein over to the TIM22 insertion machine in the inner membrane.
After binding, the small TIM chaperone complex delivers its substrate to the TIM22 complex, the inner membrane insertase that mediates membrane integration of carrier proteins. TIM9-TIM12-containing assemblies are especially important for transferring substrates to TIM22, and biochemical reconstitution has been used to capture these chaperone-substrate complexes. The handover step ensures that hydrophobic transmembrane segments are inserted into the inner membrane in the correct topology.
Inner membrane insertion and complex assembly
In simple terms: Once inserted, the carrier protein folds and assembles into its working form in the inner membrane.
TIM22 inserts the substrate into the inner membrane, after which the protein folds and assembles into functional carrier complexes. The small TIM chaperone complex is not part of the final membrane-embedded carrier; it acts catalytically to facilitate insertion and is recycled for further rounds of chaperoning. Defects in this step impair the assembly of multiple carrier proteins and reduce mitochondrial metabolic exchange.
Integration with IMS proteostasis
In simple terms: The chaperone complex works alongside other quality-control machines that keep the intermembrane space clean.
The small TIM chaperone complex operates within a broader IMS proteostasis network that includes CLPB and small heat shock proteins, which help maintain the solubility of IMS proteins. HAX1 has been reported to drive assembly and activation of the mitochondrial IMS chaperone CLPB, linking chaperone systems in this compartment. In addition, the ubiquitin-proteasome system regulates the abundance of IMS proteins, and cytosolic misfolded proteins can be imported into mitochondria as part of proteostasis control.
Key Genes Involved in GO:0042719 mitochondrial intermembrane space chaperone complex
The genes and proteins most directly associated with GO:0042719 are the small TIM chaperones and their partner import and quality-control factors.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TIM9 (TIMM9) | Core small TIM chaperone subunit forming TIM9-TIM10 and TIM9-TIM12 hexamers | Central to GO:0042719; knockout impairs carrier import |
| TIM10 (TIMM10) | Small TIM chaperone subunit of the TIM9-TIM10 particle | Required for substrate shielding and handover to TIM22 |
| TIM12 (TIMM12) | Small TIM chaperone subunit enriched in TIM9-TIM12 assemblies | Important for transfer of substrates to TIM22 |
| TIM22 (TIMM22) | Inner membrane insertase receiving substrates from small TIMs | Defines the downstream step of GO:0042719 |
| TIM23 (TIMM23) | Inner membrane translocase for matrix-targeted proteins | Context for distinguishing import pathways |
| TOM20 (TOMM20) | Outer membrane receptor for mitochondrial protein import | Upstream entry point for chaperone substrates |
| TOM40 (TOMM40) | Outer membrane channel of the TOM complex | Required for substrate entry into the IMS |
| CLPB | IMS chaperone and disaggregase | Cooperates with IMS proteostasis; HAX1 drives its assembly |
| HAX1 | Regulator of CLPB assembly and activation | Links IMS chaperone networks to disease |
| HSPB1 | Small heat shock protein acting in the IMS | Expands the IMS chaperone network |
| HSPB5 | Small heat shock protein with IMS chaperone activity | Supports IMS protein solubility |
| AAC (SLC25A4) | Mitochondrial ADP/ATP carrier, a classic small TIM substrate | Model substrate for import assays |
| SLC25A3 | Phosphate carrier, a metabolite carrier substrate | Readout for small TIM-dependent import |
| SLC25A6 | Adenine nucleotide translocator family carrier | Carrier import model |
| UBB | Ubiquitin precursor for proteasomal tagging | Links IMS protein turnover to the proteasome |
| UBC | Ubiquitin-conjugating component of proteostasis | Regulates IMS protein stability |
| VCP/p97 | AAA-ATPase in cytosolic quality control | Connects cytosolic proteostasis to mitochondrial import |
| HSPA1A | Cytosolic Hsp70 chaperone | Supports cytosolic protein handling before import |
How Is mitochondrial intermembrane space chaperone complex Regulated?
The mitochondrial intermembrane space chaperone complex is regulated at the level of subunit availability and substrate flux. The ubiquitin-proteasome system controls the abundance of IMS proteins, including small TIM components and their substrates, by targeting them for degradation when they fail to assemble or fold. Cytosolic proteostasis pathways can also route misfolded proteins into mitochondria, indirectly influencing the load on IMS chaperone systems. In addition, the IMS chaperone network is coordinated with CLPB, whose assembly and activation are driven by HAX1, and with small heat shock proteins that maintain IMS protein solubility. These layers of regulation ensure that the small TIM complex is matched to the demand for inner membrane protein insertion.
mitochondrial intermembrane space chaperone complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TIM9 (TIMM9) | Mitochondrial carrier import defect and mitochondrial dysfunction | CRISPR knockout in human cell lines with carrier import assays |
| TIM10 (TIMM10) | Impaired small TIM chaperone function and IMS proteostasis | Knockout and rescue with tagged TIM10 |
| TIM12 (TIMM12) | Defective substrate handover to TIM22 | Point-mutation knock-in of substrate-binding residues |
| CLPB | IMS proteostasis and neurodegeneration-related chaperone dysfunction | HAX1-dependent assembly assays and knockout models |
| HSPB1 | Small heat shock protein chaperone activity in the IMS | Overexpression and knockout in mitochondrial stress models |
Mitochondrial disease and carrier protein defects
Because the small TIM chaperone complex is required for the import and assembly of mitochondrial metabolite carriers, its dysfunction impairs oxidative phosphorylation and metabolite exchange. Defects in carrier biogenesis are associated with mitochondrial disease phenotypes, and small TIM components are therefore candidate modifiers of these disorders. Experimental models that disrupt GO:0042719 can be used to test whether carrier loss is the primary driver of mitochondrial dysfunction.
Neurodegeneration and IMS proteostasis
The IMS chaperone network, including small TIM proteins, CLPB and small heat shock proteins, protects against protein aggregation in a compartment that is vulnerable to oxidative stress. HAX1-dependent CLPB assembly links IMS chaperone function to cellular survival pathways relevant to neurodegeneration. Disruption of IMS proteostasis can therefore contribute to neuronal vulnerability and mitochondrial dysfunction.
Cancer metabolism
Mitochondrial metabolite carriers support the metabolic flexibility of cancer cells, and the small TIM chaperone complex is required for their biogenesis. Changes in small TIM expression or function could therefore influence cancer cell metabolism and sensitivity to mitochondrial stressors. The complex is a potential node for experimental interrogation in cancer metabolism studies.
Proteostasis and protein quality control
The ubiquitin-proteasome system regulates IMS protein levels, and the import of misfolded cytosolic proteins into mitochondria adds another layer of proteostasis control that intersects with GO:0042719. Failure of these quality-control pathways can overload IMS chaperones and impair mitochondrial function. This connection makes GO:0042719 relevant to broader studies of protein misfolding and cellular stress responses.
From mitochondrial intermembrane space chaperone complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is TIM9 required for carrier protein import? | TIM9 knockout cell line with mitochondrial import assays |
| Which residues mediate substrate binding? | Point-mutation knock-in of TIM10 or TIM12 substrate-binding residues |
| Where does the small TIM complex localize? | Tagged knock-in of TIM9 or TIM10 with fluorescent or affinity tags |
| Does overexpression of small TIMs rescue import defects? | Overexpression cell model for TIM9, TIM10 or TIM12 |
| How does HAX1 regulate CLPB in the IMS? | HAX1 knockout and overexpression with CLPB assembly readouts |
| How does proteasome inhibition affect IMS proteins? | Proteasome inhibitor treatment combined with small TIM knockout |
How to Study the mitochondrial intermembrane space chaperone complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro reconstitution | Chaperone-substrate complex formation | Defining small TIM binding and handover |
| Chemical crosslinking | Protein-protein contacts in the IMS | Mapping small TIM interactions with substrates |
| Affinity purification mass spectrometry | Interactome of the small TIM complex | Identifying substrates and partner proteins |
| Mitochondrial import assay | Efficiency of inner membrane protein insertion | Testing small TIM dependence of carrier import |
| Native gel electrophoresis | Assembly state of small TIM particles | Monitoring hexamer formation and stability |
| Fluorescence microscopy | Subcellular localization and dynamics | Visualizing IMS chaperone complexes in cells |
| Proteasome inhibition assays | Turnover of IMS proteins | Linking GO:0042719 to quality control |
| CRISPR knockout screening | Gene requirement for mitochondrial fitness | Identifying modifiers of small TIM function |
Biochemical reconstitution of chaperone-substrate complexes
Biochemical reconstitution is a powerful approach to study GO:0042719 because it allows defined chaperone-substrate complexes to be assembled and analyzed in vitro. Purified small TIM proteins can be mixed with hydrophobic carrier substrates to capture handover intermediates, and the resulting complexes can be resolved by native gel electrophoresis or crosslinking. This method directly tests the chaperone activity of the small TIM complex and its specificity for TIM22 substrates.
Proteomics and interactome mapping
Affinity purification coupled to mass spectrometry can identify the protein interaction network of the small TIM chaperone complex, including substrates and partner import factors. Proteomic profiling of IMS proteins after small TIM perturbation reveals which carrier proteins depend on the complex for stability and assembly. These datasets help define the functional footprint of GO:0042719 in mitochondrial biogenesis.
Mitochondrial import assays
In vitro and in organello import assays using radiolabeled or fluorescent substrates measure the efficiency of protein delivery to the inner membrane. By comparing wild-type and small TIM mutant mitochondria, researchers can quantify the contribution of GO:0042719 to carrier protein insertion. These assays are often combined with membrane potential measurements to distinguish import defects from general mitochondrial dysfunction.
Imaging and subcellular localization
Fluorescence microscopy of tagged small TIM proteins and substrates can visualize the distribution of the chaperone complex within the IMS and its association with the inner membrane. Super-resolution and live-cell imaging approaches can capture dynamic handover events and changes in mitochondrial morphology. These methods complement biochemical assays by providing spatial and temporal information about GO:0042719.
How CRISPR Can Be Used to Study GO:0042719 mitochondrial intermembrane space chaperone complex
Knockout
CRISPR knockout of TIM9, TIM10 or TIM12 provides a direct way to test the requirement for GO:0042719 in mitochondrial protein import and carrier assembly. Knockout cell lines can be analyzed by import assays, proteomics and respirometry to define the consequences of losing small TIM chaperone function. These models are also useful for identifying compensatory pathways that buffer against small TIM loss.
Point Mutation
Point-mutation knock-in allows precise dissection of substrate-binding surfaces and subunit interfaces within the small TIM complex. By mutating candidate residues in TIM10 or TIM12, researchers can separate chaperone binding from TIM22 handover and test structure-function hypotheses. Such models are valuable for understanding how disease-associated variants might affect GO:0042719.
Knock-in
Tagged knock-in of small TIM genes with fluorescent or affinity tags enables localization, interaction and complex-purification studies under endogenous expression conditions. Knock-in of reporter tags preserves native regulation and avoids artifacts from overexpression. These models support live-cell imaging and proteomic analysis of the small TIM chaperone complex.
Overexpression
Overexpression of small TIM subunits can test whether increased chaperone dosage rescues import defects or alters mitochondrial proteostasis. Overexpression models are also useful for producing sufficient material for biochemical reconstitution and structural studies. However, results must be interpreted carefully because excess small TIM proteins may saturate partner pathways.
How EDITGENE Supports mitochondrial intermembrane space chaperone complex Research
Researchers studying mitochondrial intermembrane space chaperone complex-related genes often need to determine whether a candidate gene is causally involved in carrier protein import, IMS proteostasis or mitochondrial disease phenotypes. EDITGENE provides CRISPR-engineered cell models and screening services that let you move from correlation to mechanism with validated knockout, point-mutation, knock-in and overexpression lines.
Contact EDITGENE today to design your custom CRISPR model for mitochondrial intermembrane space chaperone complex research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| TIMM10B Knockout HEK293 Cell Line | EDJ-KQ8541 | Human | 26515 | Details Get a Quote |
| TIMM10B Knockout HCT 116 Cell Line | EDJ-KQ33381 | Human | 26515 | Details Get a Quote |
| TIMM10B Knockout A-549 Cell Line | EDJ-KQ34686 | Human | 26515 | Details Get a Quote |
| TIMM10B Knockout HeLa Cell Line | EDJ-KQ34687 | Human | 26515 | Details Get a Quote |
| TIMM8A Knockout HEK293 Cell Line | EDJ-KQ50237 | Human | 1678 | Details Get a Quote |
| TIMM9 Knockout HEK293 Cell Line | EDJ-KQ51185 | Human | 26520 | Details Get a Quote |
| TIMM8B Knockout HEK293 Cell Line | EDJ-KQ51186 | Human | 26521 | Details Get a Quote |
| TIMM8A Knockout HeLa Cell Line | EDJ-KQ53089 | Human | 1678 | Details Get a Quote |
| TIMM9 Knockout HeLa Cell Line | EDJ-KQ55942 | Human | 26520 | Details Get a Quote |
| TIMM8B Knockout HeLa Cell Line | EDJ-KQ55943 | Human | 26521 | Details Get a Quote |
| TIMM8A Knockout A-549 Cell Line | EDJ-KQ61556 | Human | 1678 | Details Get a Quote |
| TIMM9 Knockout A-549 Cell Line | EDJ-KQ64429 | Human | 26520 | Details Get a Quote |
| TIMM8B Knockout A-549 Cell Line | EDJ-KQ64430 | Human | 26521 | Details Get a Quote |
| TIMM8A Knockout HCT 116 Cell Line | EDJ-KQ70047 | Human | 1678 | Details Get a Quote |
| TIMM9 Knockout HCT 116 Cell Line | EDJ-KQ72884 | Human | 26520 | Details Get a Quote |
Displaying Records 1 To 15 Of 16 Records
Frequently Asked Questions About mitochondrial intermembrane space chaperone complex
What is GO:0042719?
GO:0042719 is the Gene Ontology cellular component term for the mitochondrial intermembrane space chaperone complex, also called the small TIM complex, which chaperones proteins to the TIM22 complex for insertion into the mitochondrial inner membrane.
What is the mitochondrial intermembrane space chaperone complex?
It is a protein complex in the mitochondrial intermembrane space built mainly from small TIM proteins that shields hydrophobic carrier proteins and delivers them to the inner membrane insertase TIM22.
What genes are involved in the mitochondrial intermembrane space chaperone complex?
The core genes are TIM9, TIM10 and TIM12, which encode the small TIM chaperones, together with partner factors such as TIM22, CLPB and HAX1.
Where is the small TIM complex located?
The small TIM complex is located in the mitochondrial intermembrane space, where it associates with the inner membrane and the TIM22 insertase.
What proteins does the small TIM complex chaperone?
It chaperones hydrophobic inner membrane proteins, especially mitochondrial metabolite carriers such as the ADP/ATP carrier and phosphate carrier.
Why is the mitochondrial intermembrane space chaperone complex important?
It is required for the biogenesis of mitochondrial carrier proteins and therefore for oxidative phosphorylation, metabolite exchange and mitochondrial function.
How is the small TIM complex regulated?
Its subunits and substrates are regulated by the ubiquitin-proteasome system, and it cooperates with IMS chaperones such as CLPB and small heat shock proteins.
What diseases are linked to GO:0042719?
Dysfunction of the complex is linked to mitochondrial disease, neurodegeneration and altered cancer metabolism through impaired carrier protein biogenesis and IMS proteostasis.
How can I study the mitochondrial intermembrane space chaperone complex?
Common approaches include biochemical reconstitution, crosslinking, mitochondrial import assays, proteomics, imaging and CRISPR knockout or knock-in models.
Can CRISPR be used to study small TIM genes?
Yes, CRISPR knockout, point-mutation knock-in, tagged knock-in and overexpression models are widely used to dissect small TIM gene function and substrate handover.
Conclusion
GO:0042719 defines the mitochondrial intermembrane space chaperone complex, a small TIM-based machine that is essential for delivering hydrophobic carrier proteins to the TIM22 insertase and for maintaining mitochondrial inner membrane biogenesis. Its function is embedded in a broader IMS proteostasis network that includes CLPB, small heat shock proteins and ubiquitin-proteasome control, linking it to mitochondrial disease, neurodegeneration and cancer metabolism. Researchers can now dissect this complex with biochemical reconstitution, proteomics and CRISPR-engineered cell models, making GO:0042719 a tractable and impactful area for mitochondrial biology.
References
- 1. Ruan L et al.. 2017. Cytosolic proteostasis through importing of misfolded proteins into mitochondria.. Nature 543(7645):443-446 PMID: 28241148
- 2. Wiedemann N et al.. 2006. Chaperoning through the mitochondrial intermembrane space.. Mol Cell 21(2):145-8 PMID: 16427004
- 3. Horten P et al.. 2020. Biogenesis of Mitochondrial Metabolite Carriers.. Biomolecules 10(7) PMID: 32645990
- 4. Guillerm U et al.. 2024. Generation of TIM chaperone substrate complexes.. Methods Enzymol 707:391-422 PMID: 39488384
- 5. Adriaenssens E et al.. 2023. Small heat shock proteins operate as molecular chaperones in the mitochondrial intermembrane space.. Nat Cell Biol 25(3):467-480 PMID: 36690850
- 6. Lithgow T. 2000. Targeting of proteins to mitochondria.. FEBS Lett 476(1-2):22-6 PMID: 10878243
- 7. Fahie MAV et al.. 2026. HAX1 drives assembly and activation of the mitochondrial intermembrane space chaperone CLPB.. bioRxiv PMID: 42244541
- 8. Bragoszewski P et al.. 2013. The ubiquitin-proteasome system regulates mitochondrial intermembrane space proteins.. Mol Cell Biol 33(11):2136-48 PMID: 23508107
