BH3 Interacting Domain Death Agonist (Bid)

BID is a pro-apoptotic Bcl-2 protein containing only the BH3 domain. In response to apoptotic signaling, BID interacts with another Bcl-2 family protein, Bax, leading to the insertion of Bax into organelle membranes, primarily the outer mitochondrial membrane. Bax is believed to interact with, and induce the opening of the mitochondrial voltage-dependent anion channel, VDAC. Alternatively, growing evidence suggest that activated Bax and/or Bak form an oligomeric pore, MAC in the outer membrane. This results in the release of cytochrome c and other pro-apoptotic factors from the mitochondria, often referred to as mitochondrial outer membrane permeabilization, leading to activation of caspases. This defines BID as a direct activator of Bax, a role common to some of the pro-apoptotic Bcl-2 proteins containing only the BH3 domain.