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Updated: Jun 23, 2026
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Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools
Published on: July 20, 2022
Menaquinone as pool quinone in a purple bacterium.
Barbara Schoepp-Cothenet1, Clément Lieutaud, Frauke Baymann
1Laboratoire de Bioénergétique et Ingénierie des Protéines, Unité Propre de Recherche 9036, Institut Fédératif de Recherche 88, Centre National de la Recherche Scientifique, F-13402 Marseille Cedex 20, France. schoepp@ifr88.cnrs-mrs.fr
Summary
Purple bacteria use menaquinone-8 (MK-8) for light-driven electron transfer, not ubiquinone (UQ). This finding in Halorhodospira halophila reveals insights into the evolution of bioenergetic chains.
Area of Science:
- Microbiology
- Biochemistry
- Evolutionary Biology
Background:
- Purple bacteria traditionally use ubiquinone (UQ) in light-driven cyclic electron transfer.
- The role of quinones in photosynthetic reaction centers is crucial for energy conversion.
Purpose of the Study:
- To investigate the dominant quinone component in Halorhodospira halophila's photosynthetic system.
- To understand the implications of quinone usage on the evolution of bioenergetic chains in proteobacteria.
Main Methods:
- Spectroscopic analysis of photosynthetic reaction centers.
- Determination of redox potentials for key electron transfer components.
- Analysis of gene organization for the bc(1) complex.
Main Results:
- Halorhodospira halophila primarily utilizes menaquinone-8 (MK-8) instead of UQ.
- Lowered redox potentials were observed for the reaction center and Rieske center, consistent with MK function.
- Unusual gene organization for the bc(1) complex was identified.
Conclusions:
- The photosynthetic cycle in H. halophila is based on MK, challenging previous assumptions.
- This suggests a specific evolutionary pathway for bioenergetic chains, possibly driven by increasing oxygen levels.
- The transition from MK to UQ likely involved a period of bioenergetic ambivalence and adaptation of the bc(1) complex.
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