Low permeability of the mitochondrial inner membrane is critical for maintaining the mitochondrial electrochemical potential - the driving force for ATP production. Acute stress conditions, lead to the increase in the mitochondrial inner membrane permeability due to the opening of the permeability transition pore (PTP). PTP allows free movement of ions and small molecules leading to mitochondrial depolarization, ATP depletion and cell death. Recent studies suggest that C-subunit of the mitochondrial ATP synthase plays a central role in PTP. Previous work in our laboratory showed that mitochondria contain non-protein complex composed of polyhydroxybutyrate, inorganic polyphosphate and calcium that forms an ion channel with properties resembling PTP. Here we explore the possibility of interactions between these non-protein components and C-subunit during the induction of PTP.To induce PTP,isolated energized mitochondria were treated with calcium. Control mitochondria were treated with calcium either in the presence of ruthenium red, inhibitor of calcium uptake or Cyclosporin A, inhibitor of PTP. This was followed by a water-free chloroform extraction of channel forming fraction of PTP. Components of the extract were analyzed using immunoblot analysis. We found significantly increased amount of C-subunit associated with channel forming fraction extracted from mitochondria with activated PTP. In contrast, C-subunit was not detectable in the extract when Ruthenium Red was present and significantly decreased in the presence of Cyclosporin A or in the absence of calcium.These results show that C-subunit is likely an interacting partner of the pore-forming complex of polyphosphate, calcium and polyhydroxybutyrate. We hypothesize that fully functional PTP requires calcium-induced formation of the pore made of both the complexed polymers and the c-subunit of ATP synthase