Purified F-ATP synthase forms a Ca2+-dependent high-conductance channel matching the mitochondrial permeability transition pore
Andrea Urbani (Università degli Studi di Padova)
Valentina Giorgio (Università degli Studi di Padova)
Andrea Carrer (Università degli Studi di Padova)
Cinzia Franchin (Università degli Studi di Padova)
Giorgio Arrigoni (Università degli Studi di Padova)
Chimari Jiko (Kyoto University)
Kazuhiro Abe (Nagoya University)
Janna F.M. Bogers (TU Delft - Teaching & Learning Services)
Duncan G.G. McMillan (TU Delft - Applied Sciences)
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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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