Bcl2 Associated X Protein (Bax)

Bax (Bcl-2 associated x protein) is an apoptosis regulating protein of the Bcl-2 family. The ratio of Bax to Bcl-2 determines survival or death following an apoptotic stimulus. Bax is implicated in many cancers, uterine leiomyomas, and brain dysmorphology. Bax is a 21 kDa protein that accelerates apoptosis by binding to, and antagonizing the death repressor activity of Bcl-2 in vivo.

Bax normally resides in the cytoplasm, but following an apoptotic stimuli, Bax undergoes a conformational change and translocates to mitochondrial membranes, where it inserts and mediates the release of cytochrome c from the intermembrane space into the cytosol, in this manner activating caspase-3 and perpetuating the apoptotic cascade.