Figure 4. C-ring hypothesis.

Calcium, reactive oxygen species (ROS), and cellular stress signaling activation of the mitochondrial permeability transition pore and initiation of cell death through a potential pore in the c-ring. In this theory, the F₁F₀-ATPase would likely have to had cleared a lipid plug from the interior of the c-ring. CypD indicates cyclophilin D; and OSCP, oligomycin sensitive-conferring protein. Illustration credit: Ben Smith.