TIMM17B — Translocase of Inner Mitochondrial Membrane 17B
Overview
TIMM17B (Translocase of Inner Mitochondrial Membrane 17B) is an essential component of the TIM22 translocase complex that facilitates the import of nuclear-encoded proteins into the mitochondrial inner membrane. This gene encodes a critical subunit of the mitochondrial protein import machinery, playing a fundamental role in cellular energy metabolism, [mitochondrial dynamics](/mechanisms/mitochondrial-dysfunction), and [cellular homeostasis](/mechanisms/proteostasis-failure). TIMM17B has emerged as a protein of interest in [neurodegenerative diseases](/diseases/neurodegeneration) due to the central role of mitochondria in neuronal function and survival.
<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#f0f0f0; text-align:center;">TIMM17B</th></tr>
<tr><td><b>Gene Symbol</b></td><td>TIMM17B</td></tr>
<tr><td><b>Full Name</b></td><td>Translocase of Inner Mitochondrial Membrane 17B</td></tr>
<tr><td><b>Chromosomal Location</b></td><td>chrX p21.1</td></tr>
<tr><td><b>NCBI Gene ID</b></td><td>10982</td></tr>
<tr><td><b>OMIM ID</b></td><td>300260</td></tr>
<tr><td><b>Ensembl ID</b></td><td>ENSG00000146592</td></tr>
<tr><td><b>UniProt ID</b></td><td>O43571</td></tr>
<tr><td><b>Protein Length</b></td><td>170 amino acids</td></tr>
<tr><td><b>Expression</b></td><td>Ubiquitous, high in brain and muscle</td></tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/atherosclerosis" style="color:#ef9a9a">Atherosclerosis</a>, <a href="/wiki/heart-failure" style="color:#ef9a9a">Heart Failure</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">54 edges</a></td>
</tr>
</table>
</div>
Protein Structure and Function
TIM22 Translocase Complex
TIMM17B is a core component of the TIM22 complex, also known as the inner membrane import channel. This multi-subunit translocase is essential for the import of:
- Carrier proteins: Metabolic carriers (ADP/ATP translocase, phosphate carrier)
- Inner membrane proteins: Multi-pass transmembrane proteins
- Small proteins: <100 kDa inner membrane proteins
The TIM22 complex consists of:
| Component | Function |
|-----------|----------|
| TIMM22 | Central channel subunit |
| TIMM17A/B | Channel-forming subunits |
| TIMM29 | Adapter protein |
| TIMM54 | Import accessory |
TIMM17B Structure
TIMM17B contains characteristic features:
Transmembrane domains: Two helical transmembrane segments that anchor the protein in the inner membrane
Intermembrane space domain: Peripheral region facing the intermembrane space
Matrix-facing domain: Cytosolic region involved in substrate recognition
Conserved motifs: Essential for channel functionComparison with TIMM17A
TIMM17B is the paralog of TIMM17A:
- TIMM17A: Testis-specific, X-linked
- TIMM17B: Ubiquitously expressed, X-linked
Both can form functional channels, with partial redundancy, but TIMM17B is the dominant form in most tissues including the brain.
Normal Function
Mitochondrial Protein Import
The TIM22 translocase mediates the import of inner membrane proteins in a multi-step process:
Recognition: Cytosolic chaperones deliver preproteins to the TOM complex
Translocation through TOM: Passage through the outer membrane translocase
Inner membrane insertion: TIM22 complex catalyzes lateral insertion into the inner membrane
Assembly: Imported proteins fold and assemble into functional complexesImported Proteins
TIMM17B-dependent import includes critical mitochondrial proteins:
- SLC25 family: Mitochondrial carriers (AAC, PIC, OGC, etc.)
- OXPHOS subunits: Complex components of the electron transport chain
- Mitochondrial transporters: Nutrient and ion transporters
Proper TIMM17B function is essential for:
| Process | Importance |
|---------|------------|
| ATP synthesis | OXPHOS complex assembly |
| Metabolic regulation | Carrier protein import |
| Calcium handling | Mitochondrial calcium uniporters |
| Iron-sulfur cluster | Fe-S cluster assembly machinery |
Role in Neurodegeneration
Mitochondrial Dysfunction in Neurodegeneration
Mitochondrial dysfunction is a hallmark of neurodegenerative diseases. TIMM17B contributes to this through:
Alzheimer's Disease
- Energy failure: Impaired import of ATP synthase subunits
- Metabolic dysregulation: Altered carrier protein levels
- Calcium mishandling: Mitochondrial calcium transporter defects
Parkinson's Disease
- Complex I deficiency: Reduced import of complex I subunits
- Metabolic deficits: Altered mitochondrial carriers
- Alpha-synuclein interaction: Potential functional connection
Amyotrophic Lateral Sclerosis
- Respiratory chain defects: Impaired protein import
- Energy failure: Decreased ATP production
- Oxidative stress: Compromised antioxidant defenses
Huntington's Disease
- Mitochondrial dysfunction: Central pathogenic mechanism
- TIMM17B involvement: Import defects contribute to deficits
Down Syndrome Connection
TIMM17B is located on chromosome 21 and has been studied in relation to Down syndrome:
- Gene dosage: Extra copy of TIMM17B in trisomy 21
- Mitochondrial alterations: Observed in Down syndrome models
- Neurological implications: May contribute to cognitive phenotype
Mitochondrial Quality Control
TIMM17B participates in mitochondrial quality control:
Protein turnover: Import of mitochondrial proteins for replacement
Complex assembly: Proper assembly of OXPHOS complexes
Biogenesis: New mitochondrial protein incorporationExpression Pattern
Tissue Distribution
TIMM17B is expressed ubiquitously with highest levels in:
| Tissue | Expression Level |
|--------|------------------|
| Brain | High |
| Heart | Very high |
| Skeletal muscle | Very high |
| Liver | High |
| Kidney | Moderate |
| Lung | Moderate |
Brain Expression
In the brain, TIMM17B is expressed in:
- Neurons (all subtypes)
- [Astrocytes](/cell-types/astro- [Microglia](/cell-types/microglia)odendrocytes
- [Microglia](/cell-types/microglia)
Subcellularly, TIMM17B is located in:
- Mitochondrial inner membrane
- Contact sites with outer membrane
Regulation
TIMM17B expression is regulated by:
- Developmental stage: Higher in developing brain
- Energy demands: Activity-dependent regulation
- Stress responses: Altered in mitochondrial stress
Mitochondrial Import in Neurons
Neuronal Specialization
Neurons have unique mitochondrial requirements:
High energy demand: Synaptic activity requires massive ATP
Long-range transport: Mitochondria targeted to synapses
Local synthesis: On-site protein import for maintenance
Quality control: Constant turnover and replacementTIMM17B in Synaptic Function
Synaptic mitochondria rely on TIMM17B for:
- ATP supply for vesicle cycling
- Calcium buffering during neurotransmission
- Local protein synthesis at terminals
Mitochondrial Dynamics
TIMM17B intersects with mitochondrial dynamics:
- Fission: New mitochondria require protein import
- Fusion: Mixing of protein components
- Biogenesis: PGC-1α pathway and TIMM17B
Therapeutic Implications
Targeting Mitochondrial Import
Modulating TIMM17B or the TIM22 complex could influence:
Mitochondrial biogenesis: Enhance overall function
Protein quality control: Improve import efficiency
Metabolic regulation: Modulate substrate utilizationSmall Molecule Approaches
Potential therapeutic strategies include:
- Import enhancers: Compounds that accelerate protein import
- Channel modulators: Adjust TIM22 complex activity
- Chaperone mimics: Facilitate protein delivery
Gene Therapy Potential
- TIMM17B overexpression: Enhance import capacity
- Alternative splicing: Promote TIMM17A in specific contexts
Research Models
Cell Culture Studies
- Neuronal cell lines: SH-SY5Y, PC12, primary neurons
- Knockdown/knockout: siRNA, CRISPR approaches
- Overexpression: Adenoviral, lentiviral delivery
Animal Models
- Drosophila: TIM17 homolog studies
- Zebrafish: Mitochondrial import mutants
- Mice: Conditional knockouts
Key Findings from Models
- TIM17 deletion is embryonic lethal
- Partial loss causes mitochondrial dysfunction
- Neuronal-specific knockouts show neurodegeneration
Interaction Network
Core Interactors
| Protein | Interaction |
|---------|------------|
| TIMM22 | Core complex subunit |
| TIMM17A | Paralog, functional redundancy |
| TIMM54 | Import accessory |
| TIMM29 | Adapter protein |
Imported Substrates
- ADP/ATP translocase (SLC25A4/5/6)
- Phosphate carrier (SLC25A23)
- Mitochondrial carriers (SLC25 family)
- Various inner membrane proteins
- Mitochondrial protein import
- OXPHOS assembly
- Mitochondrial dynamics
- Metabolic regulation
Biomarker Potential
TIMM17B as a Biomarker
TIMM17B may serve as:
Mitochondrial function indicator: Reflects import capacity
Disease progression marker: Alters with neurodegeneration
Therapeutic response indicator: Changes with treatmentDetection Methods
- mRNA levels: qPCR from tissue/fluids
- Protein levels: Western blot, ELISA
- Activity assays: Import capacity measurements
Mechanisms
- [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction) — Energy failure
- [Proteostasis Failure](/mechanisms/proteostasis-failure) — Protein quality control
- [Oxidative Stress](/mechanisms/oxidative-stress) — ROS in neurodegeneration
- [TIMM22](/genes/timm22) — Core translocase component
- [TIMM17A](/genes/timm17a) — Paralog protein
- [TOMM20](/genes/tomm20) — Outer membrane translocase
- [PGC1A](/genes/pgc1a) — Mitochondrial biogenesis
- [TIMM22 Protein](/proteins/timm22-protein) — Translocase complex
- [TIMM23 Protein](/proteins/timm23-protein) — Related translocase
Diseases
- [Alzheimer's Disease](/diseases/alzheimers-disease) — Mitochondrial dysfunction
- [Parkinson's Disease](/diseases/parkinsons-disease) — Energy failure
- [ALS](/diseases/als) — Metabolic impairment
Research Directions
Current Understanding
- TIMM17B is essential for mitochondrial protein import
- Impaired import contributes to mitochondrial dysfunction
- Neurons are particularly vulnerable to import defects
Emerging Areas
- Single-cell analysis: Cell-type specific import capacity
- Structural biology: TIM22 complex architecture
- Therapeutic targeting: Import enhancers in development
Future Questions
- Can TIMM17B modulation slow neurodegeneration?
- What is the specific contribution to different diseases?
- Are there allele-specific effects in humans?
Key Publications
[Chacinska et al., Essential role of Tim17 in mitochondrial protein import. EMBO J. 2005](https://doi.org/10.1093/emboj/cdi318)
[Mokranjac et al., Tim23 and Tim17 form the import channel. FEBS Lett. 2003](https://doi.org/10.1016/S0014-5793(03)00442-0)
[Rehling et al., Protein insertion into mitochondria. Nat Rev Mol Cell Biol. 2004](https://doi.org/10.1038/nrm1348)
[Ishihara & Mihara, Mitochondrial protein import and human diseases. Cancer Sci. 2003](https://doi.org/10.1111/j.1349-7006.2003.tb01437.x)
[Meier et al., The mitochondrial import machinery. Trends Cell Biol. 2005](https://doi.org/10.1016/j.tcb.2005.06.003)
[Neupert & Herrmann, Mitochondrial protein import: from genes to function. Annu Rev Physiol. 2007](https://doi.org/10.1146/annurevphysiol.59.1.519)
[Wiedemann et al., The protein import machinery of mitochondria. J Cell Sci. 2004](https://doi.org/10.1242/jcs.01412)
[Chaves et al., Mitochondrial dysfunction in neurodegenerative diseases. Front Cell Neurosci. 2019](https://pubmed.ncbi.nlm.nih.gov/31151629/)
[Wang et al., Mitochondrial dysfunction and neurodegeneration. Neuropharmacology. 2021](https://doi.org/10.1016/j.neuropharm.2020.108235)See Also
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [ALS](/diseases/als)
- [Mitochondrial Diseases](/diseases/mitochondrial-diseases)
- [Mitochondrial Dynamics](/mechanisms/mitochondrial-dysfunction)
External Links
- [Ensembl: ENSG00000146592](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000146592)
- [NCBI Gene: TIMM17B](https://www.ncbi.nlm.nih.gov/gene/10982)
- [UniProt: TIMM17B](https://www.uniprot.org/uniprotkb/O43571)
- [GeneCards: TIMM17B](https://www.genecards.org/cgi-bin/carddisp.pl?gene=TIMM17B)
Related Pages
- TIMM17A - Paralog protein
- TIMM22 - Central translocase component
- TIMM23 - Related translocase subunit
- Mitochondrial protein import
References
[Chacinska et al., Essential role of Tim17 in mitochondrial protein import (2005)](https://doi.org/10.1093/emboj/cdi318)
[Mokranjac et al., Tim23 and Tim17 form the import channel (2003)]([DOI:10.1016/S0014-5793(03)00442-0](https://doi.org/10.1016/S0014-5793(03)00442-0))
[Rehling et al., Protein insertion into mitochondria (2004)](https://doi.org/10.1038/nrm1348)
[Ishihara & Mihara, Mitochondrial protein import and human diseases (2003)](https://doi.org/10.1111/j.1349-7006.2003.tb01437.x)
[Meier et al., The mitochondrial import machinery and IAM (2005)](https://doi.org/10.1016/j.tcb.2005.06.003)
[Neupert & Herrmann, Mitochondrial protein import: from genes to function (2007)](https://doi.org/10.1146/annurevphysiol.59.1.519)
[Wiedemann et al., The protein import machinery of mitochondria (2004)](https://doi.org/10.1242/jcs.01412)
[Chaves et al., Mitochondrial dysfunction in neurodegenerative diseases (2019)](https://pubmed.ncbi.nlm.nih.gov/31151629/)
[Saraste, Oxidative phosphorylation at the age of genomics (1999)]([DOI:10.1016/S0891-5849(99)00105-9](https://doi.org/10.1016/S0891-5849(99)00105-9))
[Reddy & Beal, Mitochondrial dysfunction in neurodegenerative diseases (2000)]([DOI:10.1016/S0891-5849(00)00209-9](https://doi.org/10.1016/S0891-5849(00)00209-9))
[Mattson et al., Mitochondria and neuronal calcium homeostasis (2008)](https://doi.org/10.1038/nrn2429)
[Du et al., Mitochondrial dynamics and neurodegeneration (2009)](https://doi.org/10.1016/j.neuro.2009.03.004)
[Lin & Beal, Mitochondrial quality control in neurodegeneration (2008)](https://doi.org/10.1016/j.tibs.2008.05.008)
[Tait & Green, Mitochondrial apoptosis in neurodegeneration (2010)](https://doi.org/10.1016/j.tips.2010.02.002)
[Schapira, Mitochondrial diseases (2012)]([DOI:10.1016/S0140-6736(12)61179-8](https://doi.org/10.1016/S0140-6736(12)61179-8))
[Devin & Bredesen, Mitochondria in neurodegeneration (2013)](https://doi.org/10.1016/j.biochi.2012.07.012)
[Kelley et al., Mitochondrial dynamics in brain aging (2019)](https://doi.org/10.1016/j.tics.2019.02.001)
[Misrani et al., Mitochondrial protein quality control in aging (2021)](https://doi.org/10.1016/j.arr.2021.01.006)
[Wang et al., Mitochondrial dysfunction and neurodegeneration (2021)](https://doi.org/10.1016/j.neuropharm.2020.108235)Pathway Diagram
The following diagram shows the key molecular relationships involving timm17b discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)
Pathway Diagram
The following diagram shows the key molecular relationships involving TIMM17B — Translocase of Inner Mitochondrial Membrane 17B discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)