Voltage-dependent Anion Channels Control the Release of the Superoxide Anion from Mitochondria to Cytosol

Min/mg protein, a value increased ϳ8-fold by the complex III inhibitor, antimycin A

Derick Han

2003

Scholarcy highlights

  • Min/mg protein, a value increased ϳ8-fold by the complex III inhibitor, antimycin A
  • In the absence of respiratory substrates, mitochondria supplemented with the spin trap, DMPO, did not generate any Electron Paramagnetic Resonance signal
  • Antimycin, which increases the steady-state levels of the UQO. by inhibiting electron transfer at the bc1 segment, caused a 8-fold increase of the EPR signal intensity
  • The addition of myxothiazol to antimycin-treated mitochondria resulted in a complete inhibition of the DMPO-OH signal in agreement with an expected inhibition of ubisemiquinone formation caused by myxothiazol
  • Similar to what was observed with EPR approaches, Eϩ fluorescence increased in heart mitochondria upon supplementation with substrates and antimycin A, whereas the signal was decreased by myxothiazol
  • The notion of UQO. oxidation as the source of O2. in the intermembrane space is supported by the mechanism underlying the effect of the complex III inhibitors antimycin and myxothiazol
  • In this compartment is probably determined by several competing pathways: diffusion to cytosol through voltagedependent anion channels and other outer membrane channels; reaction with cytochrome c3ϩ; and dismutation to H2O2 that is either spontaneous or catalyzed by intermembrane space Cu,Zn-SOD

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