Permeability transition pore-related changes in the proteome and channel activity of ATP synthase dimers and monomers

Monomers, dimers, and individual FOF1-ATP synthase subunits are, presumably, involved in the formation of the mitochondrial permeability transition pore (PTP), which molecular structure, however, is still unknown. We hypothesized that upon the Ca2+-dependent assembly of PTP complex, F-ATP synthase (subunits) recruits mitochondrial proteins that do not interact or weakly interact with F-ATP synthase under normal conditions. Therefore, we examined whether the PTP opening in mitochondria before the separation of supercomplexes by BN-PAGE will increases the channel stability and channel-forming capacity of isolated F-ATP synthase dimers and monomers in planar lipid membranes. Besides, we studied the specific activity and protein composition of F-ATP synthase dimers and monomers from rat liver and heart mitochondria before and after PTP opening. By contrast to our expectations, preliminary PTP opening dramatically suppressed the high-conductance channel activity of F-ATP synthase dimers and monomers and decreased their specific "in gel" activity. The decline in the channel-forming activity correlated with the reduced levels of as few as two proteins in the bands: methylmalonate-semialdehyde dehydrogenase and prohibitin 2. These data indicate that proteins accompanying F-ATP synthase may be important players in the PTP formation and stabilization.