Mitochondrial Q cycle-derived superoxide and chemiosmotic bioenergetics

We examined the intrinsic relation between two interdependent and interacted processes, namely, chemiosmotic energy coupling partition and redox signaling involved in mitochondrial respiration. The following aspects of research were conducted and discussed: generation sites and release sidedness of superoxide from the Q cycle of complex III of the mitochondrial respiratory chain; the different physiological roles of PMF components, ΔΨ and ΔpH (ΔpHS), of the Q cycle in mitochondrial superoxide generating and partitioning; and direct feedback effects of Q cycle–derived O2•− on PMF energy partition through its interaction with protons in ΔpHS to form HO2•, leading to decreasing ΔpHS and ATP synthesis due to its increasing effects of basic proton leak of mitochondria. The present experimental data give new evidence for our hypothesis of reactive oxygen species cycle cooperation with Q cycle and H+ cycle in respiratory chain in keeping PMF energy partition and its equilibrium with redox signaling regulation of mitochondrial respiration.