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Protein synthesis by isolated pea mitochondria is dependent on the activity of respiratory complex II
M L Escobar Galvis1, J F Allen, G Hâkansson
1Plant Cell Biology, Lund University, Box 7007, S-220 07 Lund, Sweden.
Abstract:
In isolated pea (Pisum sativum L.) mitochondria incorporation of 35S-methionine into newly synthesised proteins was influenced by the presence of site-specific inhibitors of the respiratory electron-transport chain. These effects were not produced by changes in the rate of respiratory electron transport itself nor by changes in ATP concentration. Protein synthesis was inhibited by inhibitors of ubiquinone reduction but not by inhibitors of ubiquinol oxidation. By the use of additional inhibitors at specific sites of the respiratory chain, different oxidation-reduction states were obtained for the different complexes in the electron-transport chain. It was found that electron transport through succinate:ubiquinone oxidoreductase (respiratory complex II) was specifically required for protein synthesis, even when all the other conditions for protein synthesis were satisfied. We suggest that a subunit of complex II, or a component closely associated with complex II, is involved in a regulatory system that couples electron transport to protein synthesis.
Insights
Plant mitochondria protein synthesis is linked to electron transport. Specifically, electron transport through respiratory complex II is essential for new protein production in pea plants, suggesting a regulatory role for this complex.
Area of Science:
- Mitochondrial biology
- Plant physiology
- Biochemistry
Background:
- Mitochondria synthesize proteins essential for cellular function.
- The respiratory electron-transport chain (ETC) is crucial for energy production.
- The interplay between ETC activity and mitochondrial protein synthesis is not fully understood.
Purpose of the Study:
- To investigate the relationship between the respiratory electron-transport chain and mitochondrial protein synthesis in isolated pea (Pisum sativum L.) mitochondria.
- To identify specific sites within the ETC that influence protein synthesis.
Main Methods:
- Isolated pea mitochondria were used.
- Site-specific inhibitors of the respiratory electron-transport chain were employed.
- 35S-methionine incorporation was measured to quantify protein synthesis.
- Changes in respiratory electron transport rates and ATP concentration were monitored.
Main Results:
- Inhibition of ubiquinone reduction, but not ubiquinol oxidation, affected protein synthesis.
- Specific oxidation-reduction states of ETC complexes were achieved using targeted inhibitors.
- Electron transport through succinate:ubiquinone oxidoreductase (respiratory complex II) was found to be specifically required for protein synthesis.
- These effects were independent of overall respiratory rate or ATP levels.
Conclusions:
- A component of respiratory complex II, or a closely associated factor, appears to regulate mitochondrial protein synthesis.
- This suggests a direct coupling mechanism between electron transport at complex II and the synthesis of new proteins within plant mitochondria.