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Updated: Jan 19, 2026

Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess
Published on: June 1, 2022
Purified F-ATP synthase forms a Ca2+-dependent high-conductance channel matching the mitochondrial permeability
Andrea Urbani1, Valentina Giorgio1,2, Andrea Carrer1
1Department of Biomedical Sciences, University of Padova, 35131, Padova, Italy.
Abstract:
The molecular identity of the mitochondrial megachannel (MMC)/permeability transition pore (PTP), a key effector of cell death, remains controversial. By combining highly purified, fully active bovine F-ATP synthase with preformed liposomes we show that Ca2+ dissipates the H+ gradient generated by ATP hydrolysis. After incorporation of the same preparation into planar lipid bilayers Ca2+ elicits currents matching those of the MMC/PTP. Currents were fully reversible, were stabilized by benzodiazepine 423, a ligand of the OSCP subunit of F-ATP synthase that activates the MMC/PTP, and were inhibited by Mg2+ and adenine nucleotides, which also inhibit the PTP. Channel activity was insensitive to inhibitors of the adenine nucleotide translocase (ANT) and of the voltage-dependent anion channel (VDAC). Native gel-purified oligomers and dimers, but not monomers, gave rise to channel activity. These findings resolve the long-standing mystery of the MMC/PTP and demonstrate that Ca2+ can transform the energy-conserving F-ATP synthase into an energy-dissipating device.
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