GO:0005744 TIM23 mitochondrial import inner membrane translocase complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0005744 describes the TIM23 complex, the inner mitochondrial membrane machinery that imports matrix-targeted preproteins using an ATP-driven motor.
• The complex contains essential Tim proteins: Tim17 and Tim23 form the translocation channel, while Tim44 transiently engages matrix Hsp70 to power import.
• Cryo-EM structures have revealed the architecture of the TIM23 complex and its coupling to the TOM complex at the outer membrane.
• Disease-causing mutations cluster in TIM23 subunits, linking the complex to neurodevelopmental and mitochondrial disease phenotypes.
• The TIM23 complex is regulated by accessory proteins such as OCIAD1 and prohibitins, which control its stability.
• TIM23 is functionally connected to PINK1-Parkin mitophagy, making it a node in mitochondrial quality control.
Description
The TIM23 mitochondrial import inner membrane translocase complex (GO:0005744) is the protein transport machinery of the mitochondrial inner membrane that typically transports proteins possessing a matrix-targeting N-terminal presequence. It is one of the central translocases that allows nuclear-encoded proteins to cross the inner membrane and reach the mitochondrial matrix, a process essential for mitochondrial biogenesis and cellular energy metabolism. The complex contains three essential Tim proteins: Tim17 and Tim23 are thought to build a preprotein translocation channel, while Tim44 interacts transiently with the matrix heat-shock protein Hsp70 to form an ATP-driven import motor. Because mitochondrial function underpins diverse cellular processes, defects in TIM23-mediated import are increasingly recognized in human disease, including neurodevelopmental disorders and mitochondrial disease. Recent structural and biochemical studies have clarified how the TIM23 complex cooperates with the TOM complex and how its stability is regulated by accessory factors. For researchers, GO:0005744 provides a precise annotation for interrogating mitochondrial protein import, and CRISPR-based models now enable causal testing of TIM23 components in health and disease.
TIM23 mitochondrial import inner membrane translocase complex At A Glance
| GO ID | GO:0005744 |
|---|---|
| GO term | TIM23 mitochondrial import inner membrane translocase complex |
| Ontology | cellular_component |
| Synonym | mitochondrial inner membrane pre-sequence translocase complex; mitochondrial inner membrane presequence translocase complex; mitochondrial inner membrane translocase complex; Tim23 complex |
| Major function | Protein transport across the mitochondrial inner membrane for matrix-targeted preproteins, using an ATP-driven import motor |
| Essential subunits | Tim17 and Tim23 (channel), Tim44 (motor coupling) |
| Subcellular location | Mitochondrial inner membrane |
| Related translocase | TIM22 translocon, which imports different inner membrane proteins |
| Disease relevance | Mutations in TIM23 complex components are associated with mitochondrial and neurodevelopmental disease |
What Is GO:0005744?
GO:0005744 refers to the protein transport machinery embedded in the mitochondrial inner membrane that imports proteins carrying a matrix-targeting N-terminal presequence. The complex includes the essential Tim proteins Tim17 and Tim23, which are thought to form the preprotein translocation channel, and Tim44, which interacts transiently with matrix Hsp70 to create an ATP-driven import motor. This definition distinguishes the TIM23 complex from other mitochondrial translocases such as the TIM22 translocon, which handles different classes of inner membrane proteins.
Why Is TIM23 mitochondrial import inner membrane translocase complex Important in Cell Biology?
The TIM23 complex is essential because most mitochondrial proteins are nuclear-encoded and must be imported across the inner membrane to reach the matrix, where they function in oxidative phosphorylation, metabolism, and mitochondrial gene expression. Without a functional TIM23 complex, matrix-targeted preproteins cannot be imported, leading to mitochondrial dysfunction that affects tissues with high energy demand. The complex is also a hub for quality control and stress signaling, as it interacts with the PINK1-Parkin mitophagy pathway and its stability is controlled by accessory proteins. Consequently, GO:0005744 is a key annotation for studies of mitochondrial biogenesis, proteostasis, and disease mechanisms.
• Enables import of matrix-targeted preproteins, a prerequisite for oxidative phosphorylation and mitochondrial metabolism.
• Contains essential Tim17, Tim23, and Tim44 subunits required for viability.
• Cooperates with the TOM complex at the outer membrane to form TOM-TIM23 supercomplexes.
• Structural studies reveal how the complex recognizes and translocates presequence-containing proteins.
• Mutations in TIM23 components are linked to mitochondrial disease and neurodevelopmental phenotypes.
• Its stability is regulated by OCIAD1 and prohibitins, connecting import to mitochondrial proteostasis.
• Interacts with PINK1-Parkin mitophagy machinery, linking import to mitochondrial quality control.
• Provides a target for CRISPR knockout, point mutation, and knock-in models to test causality in disease.
• Serves as a marker for mitochondrial inner membrane identity in proteomic and imaging studies.
• Offers a paradigm for studying ATP-driven protein translocation motors.
What Happens During TIM23 mitochondrial import inner membrane translocase complex?
Recognition and targeting of presequence-containing preproteins
In simple terms: Proteins destined for the matrix carry a tag that is recognized at the mitochondrial surface.
Matrix-targeted preproteins possess an N-terminal presequence that is recognized by receptors on the outer membrane and then handed to the TOM complex. The TIM23 complex specifically transports proteins that possess a matrix-targeting N-terminal presequence, distinguishing it from other inner membrane translocases. This targeting step ensures that only appropriate cargo engages the TIM23 machinery.
Translocation through the Tim17-Tim23 channel
In simple terms: The protein passes through a channel formed by Tim17 and Tim23 in the inner membrane.
Tim17 and Tim23 are thought to build the preprotein translocation channel of the TIM23 complex. Structural analysis of the TIM23 complex has provided insights into how the channel accommodates preproteins during translocation. The channel functions at the inner membrane, allowing preproteins to cross the lipid bilayer.
ATP-driven import motor powered by Tim44 and Hsp70
In simple terms: An ATP-powered motor pulls the protein into the matrix.
Tim44 interacts transiently with the matrix heat-shock protein Hsp70 to form an ATP-driven import motor. This motor couples ATP hydrolysis to the translocation of preproteins into the matrix. The motor is essential for efficient import and is a defining feature of the TIM23 complex.
Coordination with TOM-TIM23 supercomplex formation
In simple terms: The outer and inner membrane machines join forces to pass proteins across both membranes.
The TIM23 complex can form supercomplexes with the TOM complex, facilitating the transfer of preproteins from the outer to the inner membrane. Methods to study TOM-TIM23 supercomplex formation have been developed, highlighting the physical coupling between the two translocases. This coordination ensures efficient import across the intermembrane space.
Regulation by accessory proteins and quality control
In simple terms: Helper proteins control the stability of the import machine and link it to stress responses.
OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase, providing a layer of post-translational control. The TIM23 complex is also functionally connected to PINK1-Parkin-mediated mitophagy, as Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress. These interactions place the TIM23 complex within mitochondrial quality control networks.
Key Genes Involved in GO:0005744 TIM23 mitochondrial import inner membrane translocase complex
The following genes encode core and accessory components of the TIM23 mitochondrial import inner membrane translocase complex and related mitochondrial import machinery.
| Gene | Major Role | Research Relevance |
|---|---|---|
| TIMM23 | Core channel subunit of the TIM23 complex | Knockout and point mutation models to study import and disease mutations |
| TIMM17A | Essential channel subunit of the TIM23 complex | Target for loss-of-function studies of inner membrane import |
| TIMM17B | Paralog of TIMM17A in the TIM23 complex | Potential redundancy and tissue-specific import studies |
| TIMM44 | Couples the import motor to matrix Hsp70 | Models to dissect ATP-driven translocation |
| HSPA9 | Matrix Hsp70 that powers the import motor | Knockout and point mutation to test motor function |
| TOMM20 | Outer membrane receptor that gates PINK1 and tethers TOM-TIM23 | Models of mitophagy and mitochondrial stress |
| PINK1 | Kinase in mitophagy that interacts with TOM-TIM23 upon stress | Knockout and knock-in for Parkinson's disease research |
| PRKN | Parkin E3 ligase in PINK1-Parkin mitophagy | Models of mitochondrial quality control |
| OCIAD1 | Regulates stability of the TIM23 translocase | Knockout to study translocase turnover |
| PHB | Prohibitin that regulates TIM23 stability | Models of mitochondrial proteostasis |
| PHB2 | Prohibitin family member linked to TIM23 stability | Knockout and overexpression studies |
| TIMM22 | Component of the TIM22 translocon, distinct from TIM23 | Comparative studies of inner membrane import pathways |
| TIMM9 | Subunit of the TIM22 pathway, not TIM23 | Control for specificity of TIM23 studies |
| TIMM10 | Subunit of the TIM22 pathway, not TIM23 | Control for specificity of TIM23 studies |
| DNAJC19 | Co-chaperone associated with mitochondrial import and disease | Point mutation models for cardiomyopathy |
| MAGMAS | Mitochondrial import component linked to disease | Knockout models for mitochondrial disease |
| TIMM50 | Mitochondrial import component with disease relevance | CRISPR models for neurodevelopmental phenotypes |
How Is TIM23 mitochondrial import inner membrane translocase complex Regulated?
The TIM23 complex is regulated at multiple levels. Its stability is controlled by accessory proteins such as OCIAD1 and prohibitins, which influence the turnover of the translocase. Under mitochondrial stress, Tom20 gates PINK1 activity and mediates tethering of the TOM and TIM23 translocases, linking import regulation to mitophagy. These mechanisms ensure that protein import capacity is matched to mitochondrial quality control demands.
TIM23 mitochondrial import inner membrane translocase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TIMM23 | Mitochondrial disease and neurodevelopmental phenotypes | Knockout and point mutation cell models |
| TIMM17A | Defective inner membrane import | Knockout cells with import assays |
| PINK1 | Parkinson's disease and mitophagy | Knockout and knock-in neurons |
| PRKN | Parkinson's disease and mitochondrial quality control | Knockout and overexpression models |
| OCIAD1 | Mitochondrial proteostasis and translocase stability | Knockout and overexpression cells |
Mitochondrial disease and neurodevelopmental disorders
Mutations in components of the TIM23 complex have been identified as hotspots for disease-causing mutations, linking defective mitochondrial protein import to mitochondrial and neurodevelopmental disease. Because the complex is essential for matrix protein import, its dysfunction can impair oxidative phosphorylation and energy metabolism in high-demand tissues.
Parkinson's disease and mitophagy
The TIM23 complex interacts with the PINK1-Parkin mitophagy pathway; Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress. A unified mechanism for mitochondrial damage sensing in PINK1-Parkin-mediated mitophagy further connects TIM23 function to Parkinson's disease biology.
Cancer and mitochondrial proteostasis
Regulation of TIM23 stability by OCIAD1 and prohibitins ties the complex to mitochondrial proteostasis, a process relevant to cancer cell survival and stress adaptation. Although direct cancer links require further study, the complex is a node in mitochondrial quality control that influences cell fate.
From TIM23 mitochondrial import inner membrane translocase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is TIMM23 essential for matrix protein import? | CRISPR knockout of TIMM23 followed by import assays |
| Do disease-associated mutations impair TIM23 function? | Point mutation knock-in of TIMM23 variants |
| How does Tim44 couple Hsp70 to translocation? | Knock-in of tagged TIMM44 for interaction studies |
| What is the role of OCIAD1 in TIM23 stability? | Knockout and overexpression of OCIAD1 |
| How does PINK1 tether TOM-TIM23 upon stress? | Knockout and knock-in of PINK1 with imaging |
| Can TIM23 subunits be tagged for live-cell imaging? | Tagged knock-in of TIMM23 or TIMM17A |
How to Study the TIM23 mitochondrial import inner membrane translocase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Cryo-EM | Structure of the TIM23 complex | Mechanistic studies of translocation |
| In vitro import assay | Translocation of presequence preproteins | Testing subunit requirements |
| Affinity purification-MS | Protein interactions of TIM23 subunits | Identifying regulators and accessory factors |
| Blue native PAGE | TOM-TIM23 supercomplex formation | Studying translocase coupling |
| Live-cell imaging | Localization and dynamics of tagged TIM23 | Mitochondrial stress and mitophagy |
| CRISPR knockout screening | Fitness and import defects | Identifying essential components |
| Proteomics | Mitochondrial proteome changes | Assessing import capacity |
Structural biology of the TIM23 complex
Cryo-electron microscopy and related structural methods have revealed the architecture of the TIM23 complex and its translocation channel. Methods for studying TOM-TIM23 supercomplex formation provide complementary biochemical approaches.
Protein import assays
In vitro and in organello import assays using radiolabeled preproteins are classical methods to measure TIM23-dependent translocation and the ATP-driven import motor. These assays can be combined with knockout or point mutation models to test specific subunits.
Proteomics and interactomics
Affinity purification and mass spectrometry can identify TIM23 complex components and accessory regulators such as OCIAD1 and prohibitins. Interaction studies also capture transient partners like Hsp70 during the import cycle.
Imaging and mitophagy readouts
Fluorescence imaging of tagged TIM23 subunits and mitophagy reporters can monitor complex localization and stress-induced tethering with TOM and PINK1. These approaches link import machinery dynamics to mitochondrial quality control.
How CRISPR Can Be Used to Study GO:0005744 TIM23 mitochondrial import inner membrane translocase complex
Knockout
CRISPR knockout of TIMM23, TIMM17A, or TIMM44 can test the essentiality of TIM23 complex subunits for mitochondrial protein import and cell viability. Knockout models are also used to study accessory regulators such as OCIAD1.
Point Mutation
Point mutation knock-in of disease-associated variants in TIM23 components allows causal testing of mutations identified as hotspots for disease-causing mutations. Such models can reveal subtle import defects that are masked in complete knockouts.
Knock-in
Tagged knock-in of TIMM23 or TIMM17A enables live-cell imaging and biochemical isolation of the complex. Knock-in of interaction tags on TIMM44 facilitates studies of the ATP-driven import motor.
Overexpression
Overexpression of TIM23 subunits or regulators such as OCIAD1 can test gain-of-function effects on translocase stability and mitochondrial proteostasis. Overexpression models complement knockout studies to define dosage-sensitive roles.
How EDITGENE Supports TIM23 mitochondrial import inner membrane translocase complex Research
Researchers studying TIM23 mitochondrial import inner membrane translocase complex-related genes often need to determine whether a candidate gene is causally involved in mitochondrial protein import, stress responses, or disease phenotypes. EDITGENE provides publication-ready CRISPR cell models and screening services to interrogate GO:0005744 components with rigor and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for TIM23 mitochondrial import inner membrane translocase complex research.
Frequently Asked Questions About TIM23 mitochondrial import inner membrane translocase complex
What is GO:0005744?
GO:0005744 is the Gene Ontology term for the TIM23 mitochondrial import inner membrane translocase complex, the inner membrane machinery that imports matrix-targeted preproteins.
What genes are involved in the TIM23 mitochondrial import inner membrane translocase complex?
Core genes include TIMM23, TIMM17A, TIMM17B, and TIMM44, with accessory regulators such as OCIAD1 and prohibitins.
What does the TIM23 complex do?
It transports proteins with a matrix-targeting N-terminal presequence across the mitochondrial inner membrane using an ATP-driven import motor.
How is the TIM23 complex powered?
Tim44 interacts transiently with matrix Hsp70 to form an ATP-driven import motor that pulls preproteins into the matrix.
Is the TIM23 complex involved in disease?
Yes, mutations in TIM23 components are hotspots for disease-causing mutations linked to mitochondrial and neurodevelopmental disease.
How does the TIM23 complex relate to mitophagy?
Tom20 gates PINK1 activity and mediates tethering of the TOM and TIM23 translocases upon mitochondrial stress, linking import to PINK1-Parkin mitophagy.
What is the difference between TIM23 and TIM22?
TIM23 imports matrix-targeted presequence proteins, while the TIM22 translocon handles a different class of inner membrane proteins.
How can I study the TIM23 complex with CRISPR?
Knockout, point mutation, knock-in, and overexpression models can test subunit essentiality, disease variants, and regulatory mechanisms.
What methods are used to study TIM23?
Cryo-EM, in vitro import assays, affinity purification-mass spectrometry, blue native PAGE, and live-cell imaging are commonly used.
What regulates TIM23 stability?
OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase.
Conclusion
GO:0005744 defines the TIM23 mitochondrial import inner membrane translocase complex, a central machine for importing matrix-targeted preproteins through an ATP-driven motor. Its core subunits, structural organization, and regulation by accessory proteins make it a focal point for mitochondrial biology and disease research. CRISPR-based models and modern structural and proteomic methods now enable precise interrogation of TIM23 function in health and disease.
References
- 1. Demishtein-Zohary K et al.. 2017. The TIM23 mitochondrial protein import complex: function and dysfunction.. Cell Tissue Res 367(1):33-41 PMID: 27590886
- 2. Jain S et al.. 2024. Hotspots for Disease-Causing Mutations in the Mitochondrial TIM23 Import Complex.. Genes (Basel) 15(12) PMID: 39766801
- 3. Jain N et al.. 2024. TOM-TIM23 supercomplex formation.. Methods Enzymol 707:3-22 PMID: 39488380
- 4. Sim SI et al.. 2023. Structural basis of mitochondrial protein import by the TIM23 complex.. Nature 621(7979):620-626 PMID: 37344598
- 5. Jensen RE et al.. 2002. Protein import into and across the mitochondrial inner membrane: role of the TIM23 and TIM22 translocons.. Biochim Biophys Acta 1592(1):25-34 PMID: 12191765
- 6. Eldeeb MA et al.. 2024. Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress.. Proc Natl Acad Sci U S A 121(10):e2313540121 PMID: 38416681
- 7. Thayer JA et al.. 2026. A unified mechanism for mitochondrial damage sensing in PINK1-Parkin-mediated mitophagy.. EMBO J 45(1):64-105 PMID: 41266657
- 8. Elancheliyan P et al.. 2024. OCIAD1 and prohibitins regulate the stability of the TIM23 protein translocase.. Cell Rep 43(12):115038 PMID: 39630581
