Fig. 4. Scheme of tBid-induced Bak-mediated cytochrome c release. In the inactive state, Bak assumes a closed conformation, designated Bak. tBid induces a change in conformation to an open conformer, Bak*. Open conformers self-assemble into an outer membrane pore [Bak*]_n through which cytochrome c permeates. Bak is also activated autocatalytically by Bak*. The rate constants for tBid-induced and autocatalytic Bak* formation are c (minute^–1) and f (minute^–1), respectively. The rate constant for cytochrome c permeation from the intracristal/intermembrane spaces to the external medium is a (minute^–1).