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Updated: Feb 8, 2026

Analyzing Supercomplexes of the Mitochondrial Electron Transport Chain with Native Electrophoresis, In-gel Assays, and Electroelution
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Mitochondrial Supercomplexes Do Not Enhance Catalysis by Quinone Channeling.

Justin G Fedor1, Judy Hirst1

  • 1The Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0XY, UK.

Cell Metabolism
|June 26, 2018
PubMed
Summary

Mitochondrial supercomplexes do not require substrate channeling for respiration. Introducing an alternative quinol oxidase showed that quinones and quinols move freely, disproving channeling in electron transport chain function.

Keywords:
alternative oxidasechannelingmitochondriaoxidative phosphorylationrespirasomesupercomplexubiquinone

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Area of Science:

  • Biochemistry
  • Mitochondrial respiration
  • Electron transport chain

Background:

  • Mitochondrial respiratory supercomplexes (complexes I, III, IV) are key functional units.
  • Assembly into supercomplexes may offer stability or kinetic advantages via substrate channeling.
  • The role of substrate channeling in respiration remains controversial.

Purpose of the Study:

  • To investigate the necessity of substrate channeling in mitochondrial respiration.
  • To test whether quinone and quinol pools are sequestered within supercomplexes.
  • To determine if channeling confers kinetic advantages to the electron transport chain.

Main Methods:

  • Incorporation of an alternative quinol oxidase (AOX) into mammalian heart mitochondrial membranes.
  • Introduction of a competing pathway for quinol oxidation.
  • Assessment of NADH oxidation rates and membrane integrity.

Main Results:

  • AOX significantly increased NADH oxidation by O2 without altering membrane integrity or supercomplexes.
  • Quinol oxidation by AOX outside supercomplexes was faster than by complex III within supercomplexes.
  • Evidence suggests quinone and quinol freely diffuse in and out of supercomplexes.

Conclusions:

  • Substrate channeling does not occur within mitochondrial respiratory supercomplexes.
  • Free diffusion of quinone and quinol is sufficient for supporting respiration.
  • Channeling is not required for kinetic advantages in the electron transport chain.