Unveiling ADP-binding sites and channels in respiratory complexes: Validation of Murburn concept as a holistic explanation for oxidative phosphorylation

Abstract: Mitochondrial oxidative phosphorylation (mOxPhos) makes ATP, the energy currency of life. Chemiosmosis, a proton centric mechanism, advocates that Complex V harnesses a transmembrane potential (TMP) for ATP synthesis. This perception of cellular respiration requires oxygen to stay tethered at Complex IV (an association inhibited by cyanide) and diffusible reactive oxygen species (DROS) are considered wasteful and toxic products. With new mechanistic insights on heme and flavin enzymes, an oxygen or DROS centric explanation (called murburn concept) was recently proposed for mOxPhos. In the new mechanism, TMP is not directly harnessed, protons are a rate limiting reactant and DROS within matrix serve as the chemical coupling agents that directly link NADH oxidation with ATP synthesis. Herein, we report multiple ADP binding sites and solvent accessible DROS channels in respiratory proteins, which validate the oxygen or DROS centric power generation (ATP synthesis) system in mOxPhos. Since cyanide's heme binding Kd is high (mM), low doses (uM) of cyanide is lethal because cyanide disrupts DROS dynamics in mOxPhos. The critical study also provides comprehensive arguments against Mitchell's and Boyer's explanations and extensive support for murburn concept based holistic perspectives for mOxPhos.