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Updated: Aug 19, 2026
Isolation and Functional Analysis of Mitochondria from Cultured Cells and Mouse Tissue
Published on: March 23, 2015
Characterization of mouse nuclear and mitochondrial mutants with increased resistance to cytochrome b inhibitors
1Department of Radiation Therapy, University of Texas Medical Branch, Galveston 77550.
Abstract:
A series of mouse lines with increased resistance to respiratory inhibitors which block electron transport through the protonmotive cytochrome b of complex III have been isolated in this laboratory. We describe here the isolation of a mutant with increased resistance to HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) whose phenotype is due to a nuclear mutation. At the cellular level, there is a severe reduction in respiration with the residual oxygen consumption being resistant to inhibitors of both ubiquinol-cytochrome c oxidoreductase and cytochrome oxidase. At the mitochondrial level, there was a severe derangement in NADH oxidase activity. Electron transport through the succinate oxidase span of the respiratory chain and its coupling to oxidative phosphorylation are also reduced in this nuclear mutant but not to the same extent. It is concluded that the primary defect in the mutant lies within a nuclear gene encoding a component of complex I (NADH-ubiquinol oxidoreductase). In addition, further biochemical characterization of the mitochondrially inherited inhibitor-resistant mutants has demonstrated that they also show significant reductions in the efficiency of energy transduction and in the rate of cytochrome b electron transport.
Insights
A novel nuclear mutation causes severe defects in cellular respiration by disrupting Complex I (NADH-ubiquinol oxidoreductase). This research identifies a key component in mitochondrial electron transport and energy production.
Area of Science:
- Mitochondrial biology
- Cellular respiration
- Biochemistry
Background:
- Mitochondrial electron transport chain (ETC) is crucial for cellular energy production.
- Complex III (cytochrome bc1 complex) is a key component of the ETC, involved in proton translocation.
- Inhibitors targeting the ETC are valuable tools for studying mitochondrial function.
Purpose of the Study:
- To isolate and characterize mouse mutants with resistance to respiratory inhibitors.
- To identify the genetic basis and cellular consequences of a novel nuclear mutation affecting Complex III resistance.
- To investigate the impact of this mutation on mitochondrial respiration and energy transduction.
Main Methods:
- Isolation of mouse lines with inhibitor resistance.
- Phenotypic analysis at cellular and mitochondrial levels.
- Biochemical assays of oxygen consumption, NADH oxidase activity, and electron transport.
Main Results:
- A nuclear mutant resistant to HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) was isolated.
- The mutant exhibits severely reduced respiration, with residual oxygen consumption resistant to Complex III and IV inhibitors.
- Mitochondrial assays revealed deranged NADH oxidase activity and reduced electron transport through Complex I.
Conclusions:
- The primary defect in the mutant is a nuclear gene mutation affecting a Complex I component.
- This mutation significantly impairs mitochondrial respiration and energy transduction.
- Mitochondrially inherited mutations also reduce energy transduction efficiency and cytochrome b electron transport.
