Quinidine partially blocks mitochondrial voltage-dependent anion channel (VDAC).

Quinidine is an antiarrhythmic drug commonly used for the treatment of cardiac ailments. It affects oxidative phosphorylation, calcium uptake, and ion channels of mitochondria. We have investigated the interaction of Quinidine and mitochondrial voltage-dependent anion channel (VDAC). VDAC was purified from neuronal tissue of Wistar rats and in vitro bilayer electrophysiology experiments were performed on it. 50-mM Quinidine treatment on VDAC leads to a sudden drop in its conductance. The dose of Quinidine leading to a half-maximal current through a single-channel VDAC was calculated using Quinidine at different concentrations. In silico molecular docking studies using Autodock-4.2 software indicate interaction between Quinidine and VDAC. Docking results demonstrate the interaction of Quinidine and VDAC on its Glutamic acid residue (Glu-206 of VDAC). Fluorescence spectroscopy results on Quinidine and Glutamic acid interaction show an increase in the intensity and wavelength of Quinidine fluorescence, whereas no interaction between Quinidine and Cysteine was observed. This further supports the Glutamic acid and Quinidine interaction. In conclusion, we report Quinidine partially blocks VDAC due to the interaction of Glutamic acid and Quinidine in the channel pore.