Bak or Bcl2 homologous antagonist is a member of the Bcl2 family of proteins. The Bcl-2 related proteins interact with one another through the formation of homo and heterodimers. The susceptibility of cells to apoptotic stimuli is thought to be controlled by the relative ratios of the different Bcl2 family proteins. Bak has been demonstrated to accelerate the rate of apoptosis in growth factor deprived murine lymphoid, neuronal and fibroblastic cell lines. This protein localizes to mitochondria, and functions to induce apoptosis. It interacts with and accelerates the opening of the mitochondrial voltage-dependent anion channel, which leads to a loss in membrane potential and the release of cytochrome c. Bak also interacts with the tumor suppressor P53 after exposure to cell stress.