BAK1 (BCL2 antagonist/killer 1) belongs to the BCL2 protein family. BCL2 family members form oligomers or heterodimers and act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities. BAK1 localizes to mitochondria, and functions to induce apoptosis. BAK1 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. It also interacts with the tumor suppressor P53 after exposure to cell stress.