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Anaerobic Protein Purification and Kinetic Analysis via Oxygen Electrode for Studying DesB Dioxygenase Activity and Inhibition
Published on: October 3, 2018
Structure/function of oxygen-regulated isoforms in cytochrome c oxidase
1Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA.
The Journal of Experimental Biology
|May 29, 1998
Summary
Oxygen levels regulate yeast cytochrome c oxidase activity by controlling the assembly of holoenzyme molecules and the expression of specific subunit V isoforms. This ensures cells adapt their energy production to varying oxygen conditions.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Respiration
Background:
- Eukaryotic cytochrome c oxidase is a crucial enzyme complex for cellular respiration.
- It comprises subunits encoded by both nuclear and mitochondrial genomes.
- Nuclear-encoded subunits can arise from multigene families, leading to tissue-specific or environmentally regulated isoforms.
Purpose of the Study:
- To investigate the differential regulation of cytochrome c oxidase subunit V isoforms by oxygen concentration in yeast (Saccharomyces cerevisiae).
- To understand how these isoforms affect the enzyme's catalytic properties and overall activity.
- To explore the mechanisms of oxygen-dependent control over holoenzyme assembly.
Main Methods:
- Analysis of gene expression regulation in response to low oxygen concentrations.
- Biochemical characterization of catalytic properties of different holoenzyme isoenzymes.
- Computational modeling to elucidate subunit interactions.
Main Results:
- Yeast subunit V isoforms (Va and Vb) are switched on/off at very low oxygen levels (0.5-1 micromol l-1 O2).
- The 'hypoxic' isoform (Vb) enhances catalytic constant 3-4 fold over the 'aerobic' isoform (Va) by altering electron transfer.
- Oxygen also regulates transcription of other nuclear-coded subunits and post-transcriptional levels of mitochondrial subunits I and II.
Conclusions:
- Oxygen-regulated isoforms of subunit V allow for the assembly of different holoenzyme isoenzymes in yeast.
- Cellular cytochrome c oxidase activity is modulated by both the quantity of holoenzyme and the specific isoforms present.
- This regulatory mechanism provides a means for yeast to adapt energy metabolism to fluctuating oxygen availability.
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