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Effects of rotenone and pyridaben on complex I electron transfer and on mitochondrial nitric oxide synthase

Ana Navarro1, Manuel J Bández, Carmen Gómez

  • 1Department of Biochemistry and Molecular Biology, School of Medicine, University of Cádiz, Plaza Fragela 9, 11003 Cádiz, Spain. ana.navarro@uca.es

Journal of Bioenergetics and Biomembranes
|October 2, 2010
PubMed

Insights

Rotenone and pyridaben selectively inhibit rat brain mitochondrial complex I and respiration. This suggests mitochondrial nitric oxide synthase (mtNOS) is near complex I, with binding strength dependent on membrane potential.

Area of Science:

  • Biochemistry
  • Mitochondrial Physiology
  • Neuroscience

Background:

  • Mitochondria are crucial for cellular energy production and signaling.
  • Mitochondrial nitric oxide synthase (mtNOS) plays a role in regulating mitochondrial function.
  • Understanding inhibitor interactions with mitochondrial components is key to deciphering cellular processes.

Purpose of the Study:

  • To investigate the inhibitory effects of rotenone and pyridaben on rat brain mitochondrial activities.
  • To determine the inhibitory constants (Ki) and maximal inhibition (Imax) for these compounds.
  • To elucidate the relationship between mtNOS activity and mitochondrial complex I.

Main Methods:

  • Assay of mitochondrial complexes I, II, and IV activities.
  • Measurement of mitochondrial respiration in states 3, 3u, and 4.
  • Assessment of biochemical and functional mtNOS activities and inner membrane potential.
  • Determination of inhibitor concentration for half-maximal inhibition (Ki).

Main Results:

  • Rotenone and pyridaben selectively inhibited complex I activity, mitochondrial respiration, and membrane potential with a Ki of 0.28-0.36 nmol/mg protein.
  • Functional mtNOS activity was half-inhibited at 0.70-0.74 nmol/mg protein (state 3) and 2.52-2.98 nmol/mg protein (state 3u).
  • Inhibitor binding to mtNOS was stronger at high membrane potential (Δψ) and weaker at low Δψ.

Conclusions:

  • Rotenone and pyridaben act as potent inhibitors of mitochondrial complex I and respiration in rat brain mitochondria.
  • The results suggest a close structural proximity between mtNOS and complex I.
  • A hydrophobic interaction between mtNOS and complex I is proposed, with binding affinity modulated by the inner membrane potential.

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