(D) Parkin-mediated ubiquitination limits BAK apoptotic activity. BAK-/-BAX-/- HeLa cells expressing Parkin and BAK were treated with AO (2 h) prior to isolation of mitochondria and treatment with recombinant cBID and analysis of cytochrome c release. Immunoblots are representative of three independent experiments. Graph shows densitometric analysis of three independent experiments or cytochrome c in the supernatant fraction. Error bars represent mean +/- SD. 