GO:0008137 NADH dehydrogenase (ubiquinone) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008137 describes the molecular function that catalyzes electron transfer from NADH to ubiquinone, the defining catalytic activity of mitochondrial complex I.
• This activity is the entry point of the respiratory chain and is essential for ATP production, redox balance, and metabolic signaling.
• Complex I is a large multi-subunit assembly; its activity depends on coordinated expression and assembly of nuclear- and mitochondrial-encoded subunits.
• Dysregulation of this activity is linked to cardiomyopathy, metabolic disorders, and tumor growth, making it a target for mechanistic and therapeutic studies.
• CRISPR-based knockout, point mutation, knock-in, and overexpression models enable causal dissection of complex I subunit function.
• EDITGENE provides end-to-end cell model and screening services to study GO:0008137 in disease and drug discovery contexts.
Description
NADH dehydrogenase (ubiquinone) activity (GO:0008137) is the catalytic function of mitochondrial respiratory complex I, which transfers electrons from NADH to ubiquinone while pumping protons across the inner mitochondrial membrane. This activity is the first and rate-limiting step of the mitochondrial electron transport chain and is therefore central to cellular energy metabolism, redox homeostasis, and metabolic signaling. Researchers study GO:0008137 to understand how mitochondrial dysfunction contributes to disease and to identify targets for therapeutic intervention. The reaction is carried out by a large multi-subunit enzyme whose assembly and activity are tightly regulated by nutrient and stress signals. Because complex I dysfunction is implicated in cardiomyopathy, metabolic disorders, and cancer, precise genetic models are needed to dissect the causal roles of individual subunits.
NADH dehydrogenase (ubiquinone) activity At A Glance
| GO ID | GO:0008137 |
|---|---|
| GO term | NADH dehydrogenase (ubiquinone) activity |
| Ontology | molecular_function |
| Synonym | complex I (electron transport chain) activity; NADH:ubiquinone oxidoreductase activity; ubiquinone reductase activity |
| Major function | Catalyzes electron transfer from NADH to ubiquinone, the first step of the mitochondrial respiratory chain |
| Reaction | NADH + ubiquinone + 5 H+(in) = NAD+ + ubiquinol + 4 H+(out) |
| Cellular location | Inner mitochondrial membrane, as part of respiratory complex I |
| Related processes | Oxidative phosphorylation, mitochondrial ATP synthesis, redox signaling |
| Disease relevance | Cardiomyopathy, metabolic disorders, cancer, mitochondrial dysfunction |
What Is GO:0008137?
GO:0008137 describes the catalysis of the reaction: NADH + ubiquinone + 5 H+(in) = NAD+ + ubiquinol + 4 H+(out). In other words, it is the enzymatic activity that oxidizes NADH, reduces ubiquinone to ubiquinol, and couples this redox reaction to proton translocation across the inner mitochondrial membrane.
Why Is NADH dehydrogenase (ubiquinone) activity Important in Cell Biology?
GO:0008137 is essential because it defines the catalytic core of mitochondrial complex I, the largest respiratory chain enzyme and a major site of reactive oxygen species production and metabolic regulation. Its activity determines the rate of NADH oxidation and ubiquinone reduction, directly influencing ATP synthesis, cellular redox state, and biosynthetic pathways. Dysregulation of this activity has been linked to cardiac hypertrophy, dilated cardiomyopathy, lipid metabolism disorders, and tumor growth, making it a high-value target for both mechanistic research and drug discovery.
• Provides the primary entry point for electrons into the mitochondrial respiratory chain.
• Couples redox chemistry to proton pumping, contributing to the mitochondrial membrane potential.
• Regulates cellular NAD+/NADH ratios and redox homeostasis.
• Is required for efficient oxidative phosphorylation and ATP production.
• Its dysfunction is associated with cardiomyopathy and heart failure.
• Modulation of complex I activity affects lipid metabolism and metabolic disorders.
• Complex I activity is necessary for tumor growth in certain cancer models.
• Assembly and activity are regulated by nutrient and stress signaling pathways.
• It is a target for pharmacological agents such as metformin and berberine.
• CRISPR models enable causal testing of subunit-specific contributions to disease.
What Happens During NADH dehydrogenase (ubiquinone) activity?
Electron transfer from NADH to ubiquinone
In simple terms: Complex I takes electrons from NADH and hands them to ubiquinone.
The catalytic cycle begins when NADH binds to the hydrophilic arm of complex I and donates two electrons to the flavin mononucleotide (FMN) cofactor. These electrons are then transferred through a chain of iron-sulfur clusters to the ubiquinone-binding site, where ubiquinone is reduced to ubiquinol. This redox reaction is the defining activity of GO:0008137 and is essential for respiratory chain function.
Proton translocation and energy coupling
In simple terms: As electrons move, the enzyme pumps protons across the membrane to store energy.
The energy released by the redox reaction is used to pump protons from the mitochondrial matrix to the intermembrane space, contributing to the proton motive force. This coupling of electron transfer to proton translocation is a hallmark of complex I and is required for efficient ATP synthesis by ATP synthase. The stoichiometry of the reaction reflects the movement of five protons inward and four protons outward per NADH oxidized.
Assembly and regulation of complex I
In simple terms: Many proteins must come together to build a working complex I, and this process is controlled by cellular signals.
Complex I is a multi-subunit enzyme composed of nuclear- and mitochondrial-encoded proteins that must be assembled in a coordinated manner. Nutrient and stress signals, such as the PERK-eIF2α axis, promote the assembly of respiratory chain supercomplexes that include complex I, thereby influencing its activity. Post-translational modifications, including phosphorylation of subunits such as NDUFV1, can regulate complex I function in response to physiological stress.
Integration with cellular metabolism
In simple terms: Complex I activity is connected to how cells use nutrients and make building blocks.
By oxidizing NADH, complex I regenerates NAD+, which is required for glycolysis, the TCA cycle, and other metabolic reactions. Its activity influences the balance between oxidative phosphorylation and other metabolic pathways, and it is modulated by pharmacological agents such as metformin and berberine. In cancer cells, ubiquinol oxidation by complex I is necessary for tumor growth, highlighting its role beyond energy production.
Key Genes Involved in GO:0008137 NADH dehydrogenase (ubiquinone) activity
The following genes encode subunits or regulators of the complex I holoenzyme that carries GO:0008137 activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| NDUFS2 | Core subunit of the Q-module; binds ubiquinone | Alternative splicing linked to dilated cardiomyopathy |
| NDUFV1 | Flavoprotein subunit; binds FMN and NADH | Phosphorylation by SBK2 limits cardiac hypertrophy |
| NDUFS1 | Core subunit of the Q-module | Mutations associated with mitochondrial disease |
| NDUFV2 | Accessory subunit; stabilizes complex I | Implicated in metabolic and cardiac phenotypes |
| NDUFA9 | Accessory subunit; assembly and stability | Target for complex I disassembly studies |
| NDUFB8 | Accessory subunit; supercomplex formation | Marker of complex I abundance |
| NDUFA13 | Accessory subunit; ROS regulation | Linked to metabolic stress responses |
| MT-ND1 | Mitochondrial-encoded core subunit | Mutations cause Leber hereditary optic neuropathy |
| MT-ND2 | Mitochondrial-encoded core subunit | Associated with mitochondrial disease |
| MT-ND4 | Mitochondrial-encoded core subunit | Common mutation site in mitochondrial disorders |
| MT-ND5 | Mitochondrial-encoded core subunit | Implicated in mitochondrial encephalomyopathy |
| MT-ND6 | Mitochondrial-encoded core subunit | Linked to complex I deficiency |
| NDUFAF1 | Assembly factor | Required for complex I assembly |
| NDUFAF2 | Assembly factor | Mutations cause complex I deficiency |
| NDUFAF3 | Assembly factor | Essential for early assembly steps |
| NDUFAF4 | Assembly factor | Defects lead to mitochondrial disease |
| PTBP1 | RNA-binding protein regulating NDUFS2 splicing | Modulates complex I activity in cardiomyopathy |
| SBK2 | Kinase phosphorylating NDUFV1 | Regulates complex I in cardiac hypertrophy |
How Is NADH dehydrogenase (ubiquinone) activity Regulated?
Complex I activity is regulated at multiple levels. Nutrient and stress signals, such as the PERK-eIF2α axis, promote the assembly of respiratory chain supercomplexes that include complex I, thereby enhancing its activity. Post-translational modifications, including phosphorylation of NDUFV1 by SBK2, can modulate complex I function in response to cardiac stress. Pharmacological agents such as metformin activate AMPK and improve mitochondrial respiratory activity, indirectly influencing complex I. Additionally, the cAMP cascade has been implicated in regulating the mammalian complex I.
NADH dehydrogenase (ubiquinone) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| NDUFS2 | Dilated cardiomyopathy | Knockout or point mutation in cardiomyocytes |
| NDUFV1 | Cardiac hypertrophy | Phospho-mutant knock-in in mouse heart |
| MT-ND1 | Leber hereditary optic neuropathy | Cybrid cells with mitochondrial mutation |
| NDUFAF2 | Complex I deficiency | Knockout in patient fibroblasts |
| NDUFB8 | Metabolic stress | Overexpression in liver cells |
Complex I dysfunction in cardiomyopathy
Dysregulation of complex I subunits is linked to cardiac hypertrophy and dilated cardiomyopathy. The lncRNA DCRT protects against dilated cardiomyopathy by preventing NDUFS2 alternative splicing through binding to PTBP1, thereby maintaining complex I activity. SBK2-driven phosphorylation of NDUFV1 limits cardiac hypertrophy, indicating that post-translational regulation of complex I is cardioprotective.
Metabolic disorders and complex I modulation
Complex I activity is modulated by anti-diabetic agents. Metformin improves mitochondrial respiratory activity through AMPK activation, which can enhance complex I function. Berberine alleviates lipid metabolism disorders via inhibition of mitochondrial complex I in gut and liver, demonstrating that partial inhibition can have therapeutic benefits. Pioglitazone leads to inactivation and disassembly of complex I, further highlighting the pharmacological sensitivity of this enzyme.
Complex I in cancer
Mitochondrial ubiquinol oxidation by complex I is necessary for tumor growth in certain cancer models. This dependency suggests that targeting GO:0008137 activity could be a therapeutic strategy in cancers with high oxidative phosphorylation demand.
From NADH dehydrogenase (ubiquinone) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of NDUFS2 affect complex I activity? | CRISPR knockout in cardiomyocytes |
| Does NDUFV1 phosphorylation regulate cardiac hypertrophy? | Point mutation knock-in in mouse |
| Can overexpression of NDUFB8 rescue supercomplex assembly? | Overexpression cell line |
| Does a mitochondrial DNA mutation impair complex I? | Cybrid model with MT-ND1 mutation |
| Does pharmacological inhibition of complex I alter lipid metabolism? | Knockout or knockdown in hepatocytes |
| Does complex I activity drive tumor growth? | Inducible knockout in cancer xenografts |
How to Study the NADH dehydrogenase (ubiquinone) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Spectrophotometric NADH oxidation assay | Complex I enzymatic activity | Quantify GO:0008137 in mitochondria |
| BN-PAGE immunoblotting | Complex I assembly and supercomplexes | Assess assembly defects |
| Seahorse respirometry | Oxygen consumption rate | Measure oxidative phosphorylation |
| CRISPR knockout | Loss-of-function of a subunit | Test causal role in disease |
| Phospho-specific immunoblotting | Post-translational modifications | Study NDUFV1 phosphorylation |
| Metabolomics | NAD+/NADH and lipid levels | Evaluate metabolic impact |
| Xenograft tumor growth | Tumor proliferation in vivo | Test complex I dependency |
Measuring complex I activity
Enzymatic activity of GO:0008137 is typically measured using spectrophotometric assays that monitor NADH oxidation or ubiquinone reduction in isolated mitochondria or membrane fractions. These assays can be coupled with inhibitors to distinguish complex I from other dehydrogenases.
Assessing assembly and supercomplex formation
Blue native polyacrylamide gel electrophoresis (BN-PAGE) followed by immunoblotting can resolve intact complex I and respiratory supercomplexes, providing information on assembly state and stability. This method is useful for evaluating the impact of genetic perturbations on complex I assembly.
Genetic and pharmacological perturbation
CRISPR-Cas9 knockout, point mutation, and overexpression models allow causal testing of specific subunits or regulatory sites. Pharmacological agents such as metformin, berberine, and pioglitazone can be used to modulate complex I activity in cells and animal models.
Metabolic and phenotypic readouts
Seahorse extracellular flux analysis measures oxygen consumption rate, reflecting oxidative phosphorylation and complex I activity. Metabolomics and lipidomics can reveal downstream effects on NAD+/NADH ratios and lipid metabolism.
How CRISPR Can Be Used to Study GO:0008137 NADH dehydrogenase (ubiquinone) activity
Knockout
CRISPR knockout of nuclear-encoded complex I subunits such as NDUFS2 or NDUFAF2 can abolish GO:0008137 activity, providing a clean loss-of-function model to study downstream effects on metabolism and disease. These models are useful for validating subunit essentiality and identifying compensatory pathways.
Point Mutation
Point mutations can be introduced to mimic disease-associated variants or to test the function of specific residues, such as phosphorylation sites on NDUFV1. This approach allows precise dissection of regulatory mechanisms without completely eliminating the protein.
Knock-in
Knock-in of tagged or mutant alleles enables tracking of complex I subunits in live cells and tissues, as well as conditional regulation of expression. For example, a fluorescent tag on NDUFB8 can be used to monitor assembly and localization.
Overexpression
Overexpression of complex I subunits or assembly factors can rescue deficiencies or enhance activity, providing gain-of-function models to test sufficiency in disease phenotypes. This is particularly useful for studying cardioprotective or metabolic effects.
How EDITGENE Supports NADH dehydrogenase (ubiquinone) activity Research
Researchers studying NADH dehydrogenase (ubiquinone) activity-related genes often need to determine whether a candidate gene is causally involved in mitochondrial function, metabolic regulation, or disease progression. EDITGENE provides a comprehensive suite of CRISPR-based cell model services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for NADH dehydrogenase (ubiquinone) activity research.
Frequently Asked Questions About NADH dehydrogenase (ubiquinone) activity
What is NADH dehydrogenase (ubiquinone) activity?
It is the enzymatic activity of mitochondrial complex I that catalyzes the transfer of electrons from NADH to ubiquinone, coupled to proton translocation.
What genes are involved in NADH dehydrogenase (ubiquinone) activity?
Genes encoding complex I subunits such as NDUFS2, NDUFV1, NDUFS1, and mitochondrial-encoded MT-ND1 through MT-ND6, as well as assembly factors like NDUFAF1-4.
What is the GO ID for NADH dehydrogenase (ubiquinone) activity?
GO:0008137.
How is complex I activity measured?
Common methods include spectrophotometric NADH oxidation assays, BN-PAGE for assembly, and Seahorse respirometry for oxidative phosphorylation.
What diseases are associated with complex I dysfunction?
Dilated cardiomyopathy, cardiac hypertrophy, metabolic disorders, and cancer have been linked to altered complex I activity.
Can CRISPR be used to study complex I genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect subunit function and regulation.
What is the role of NDUFS2 in complex I?
NDUFS2 is a core subunit that binds ubiquinone; its alternative splicing is linked to dilated cardiomyopathy.
How does metformin affect complex I?
Metformin improves mitochondrial respiratory activity through AMPK activation, indirectly influencing complex I function.
Is complex I activity important for cancer?
Yes, ubiquinol oxidation by complex I is necessary for tumor growth in certain cancer models.
What model systems are used to study GO:0008137?
Cell lines with CRISPR modifications, patient-derived fibroblasts, cybrids, and mouse models are commonly used.
Conclusion
NADH dehydrogenase (ubiquinone) activity (GO:0008137) is the defining catalytic function of mitochondrial complex I and is central to energy metabolism, redox balance, and cellular signaling. Its dysfunction is implicated in a range of human diseases, from cardiomyopathy to cancer, making it a critical target for mechanistic and therapeutic research. Advances in CRISPR-based cell modeling and screening now enable precise dissection of the genes and pathways that regulate this activity, offering new opportunities for drug discovery and personalized medicine.
References
- 1. Papa S et al.. 2002. The NADH: ubiquinone oxidoreductase (complex I) of the mammalian respiratory chain and the cAMP cascade.. J Bioenerg Biomembr 34(1):1-10 PMID: 11860175
- 2. Wang Y et al.. 2019. Metformin Improves Mitochondrial Respiratory Activity through Activation of AMPK.. Cell Rep 29(6):1511-1523.e5 PMID: 31693892
- 3. Balsa E et al.. 2019. ER and Nutrient Stress Promote Assembly of Respiratory Chain Supercomplexes through the PERK-eIF2α Axis.. Mol Cell 74(5):877-890.e6 PMID: 31023583
- 4. Du H et al.. 2024. LncRNA DCRT Protects Against Dilated Cardiomyopathy by Preventing NDUFS2 Alternative Splicing by Binding to PTBP1.. Circulation 150(13):1030-1049 PMID: 38841852
- 5. Yu M et al.. 2021. Berberine alleviates lipid metabolism disorders via inhibition of mitochondrial complex I in gut and liver.. Int J Biol Sci 17(7):1693-1707 PMID: 33994854
- 6. García-Ruiz I et al.. 2013. Pioglitazone leads to an inactivation and disassembly of complex I of the mitochondrial respiratory chain.. BMC Biol 11:88 PMID: 23915000
- 7. Martínez-Reyes I et al.. 2020. Mitochondrial ubiquinol oxidation is necessary for tumour growth.. Nature 585(7824):288-292 PMID: 32641834
- 8. Sun Y et al.. 2026. SBK2-Driven NDUFV1 Phosphorylation and Translocation Limits Cardiac Hypertrophy.. Circ Res 139(2):e328547 PMID: 42153297
