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Related Concept Videos

Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
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The mitochondrial cristae membrane is the primary site for the oxidative phosphorylation (OXPHOS) process of energy conversion mediated through respiratory complexes I to V. These complexes have been widely studied for decades, and it has been proven that they form supramolecular structures called respiratory supercomplexes (SC). These higher-order complexes may be crucial in maintaining the biochemical structure and improving the physiological activity of the individual complexes while...
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Electron Transport Chain: Complex I and II01:46

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Updated: Jul 6, 2026

Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools
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Published on: July 20, 2022

Mitochondrial Complex I superoxide production is attenuated by uncoupling.

Andrea Dlasková1, Lydie Hlavatá, Jan Jezek

  • 1Department of Membrane Transport Biophysics, No. 75, Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, Prague 14220, Czech Republic. dlaskova@biomed.cas.cz

The International Journal of Biochemistry & Cell Biology
|March 25, 2008
PubMed
Summary
This summary is machine-generated.

Mitochondrial Complex I superoxide production can be reduced by uncoupling, which speeds up proton pumping. However, inhibiting this pumping prevents superoxide reduction, revealing Complex I

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Isolation of Mitochondria for Mitochondrial Supercomplex Analysis from Small Tissue and Cell Culture Samples
05:45

Isolation of Mitochondria for Mitochondrial Supercomplex Analysis from Small Tissue and Cell Culture Samples

Published on: May 3, 2024

Area of Science:

  • Mitochondrial biochemistry
  • Cellular respiration
  • Oxidative stress

Background:

  • Mitochondrial Complex I (NADH:quinone oxidoreductase) is crucial for cellular respiration but generates superoxide as a byproduct.
  • The precise conditions influencing Complex I-mediated superoxide production and its regulation by membrane potential remain unclear.
  • Understanding these factors is vital for addressing mitochondrial dysfunction and oxidative stress.

Purpose of the Study:

  • To investigate whether Complex I-derived superoxide generation during forward electron transport is sensitive to membrane potential or protonmotive force.
  • To identify conditions that maximize or attenuate superoxide production by Complex I.
  • To characterize the effects of specific inhibitors on Complex I activity and superoxide generation.

Main Methods:

  • Isolated rat liver mitochondria were used to assess total mitochondrial superoxide production.
  • Amplex Red assay was employed for hydrogen peroxide (H2O2) monitoring.
  • Experiments were conducted under State 3 and State 4 respiration conditions using Complex I substrates (glutamate and malate) and Complex I + II substrates, with and without uncouplers (FCCP) and inhibitors (5-(N-ethyl-N-isopropyl) amiloride).

Main Results:

  • Uncoupling significantly diminished rotenone-induced H2O2 production in both State 3 and State 4 respiration.
  • 5-(N-ethyl-N-isopropyl) amiloride was identified as a potent inhibitor of Complex I proton pumping (IC50 = 27 µM) without affecting overall respiration.
  • This inhibitor partially or completely prevented the uncoupling-induced suppression of rotenone-induced H2O2 production, depending on the respiratory substrates used.

Conclusions:

  • Mitochondrial Complex I superoxide production can be attenuated by uncoupling, which enhances Complex I proton pumping due to respiratory control.
  • When Complex I proton pumping acceleration is blocked by 5-(N-ethyl-N-isopropyl) amiloride, superoxide production is not attenuated by uncoupling.
  • These findings highlight the role of proton motive force and Complex I proton pumping activity in regulating mitochondrial superoxide generation.