BID is a pro-apoptotic “BH3 domain-only” member of the Bcl-2 family originally discovered to interact with both the anti-apoptotic family member Bcl-2 and the pro-apoptotic protein Bax. Translocation of BID is associated with release of cytochrome c from the mitochondria, leading to complex formation with Apaf-1 and caspase-9 and resulting in caspase-9 activation.BID is localized predominantly in the cytosol and is also present in membrane fractions. It is highly expressed in kidney and can also be detected in brain, spleen, liver, testis and lung.
