Redox state of coenzyme Q10 determines its membrane localization

Area of Science:

• Biochemistry
• Biophysics
• Membrane Biology

Background:

• Coenzyme Q 10 (CoQ10) exists in oxidized (ubiquinone-10) and reduced (ubiquinol-10) forms.
• CoQ10 plays a vital role in cellular energy production and acts as an antioxidant.
• Understanding CoQ10's interaction with cell membranes is crucial for its biological function.

Purpose of the Study:

• To investigate the differential interactions of ubiquinone-10 and ubiquinol-10 with dimyristoylphosphatidylcholine (DMPC) lipid bilayers.
• To elucidate how these interactions affect membrane structure, dynamics, and phase transitions.

Main Methods:

• Differential scanning microcalorimetry (DSC) to study phase transitions.
• X-ray diffraction to analyze membrane structure and spacing.
• Infrared spectroscopy to probe lipid chain conformation.
• (2)H Nuclear Magnetic Resonance ((2)H NMR) to assess lipid motion and membrane order.

Main Results:

• Ubiquinol-10 caused greater perturbation of the DMPC phase transition compared to ubiquinone-10.
• Both forms increased membrane thickness below the phase transition, but ubiquinol-10 induced a greater loss of lipid packing order.
• Infrared and NMR data indicated increased lipid chain disorder and altered motion, particularly with ubiquinol-10, suggesting deeper bilayer penetration.

Conclusions:

• Ubiquinone-10 primarily localizes in the hydrophobic core of the lipid bilayer.
• Ubiquinol-10 interacts more extensively with phospholipid acyl chains, potentially spanning the bilayer.
• The distinct interactions of ubiquinone-10 and ubiquinol-10 influence membrane properties differently.