(E) Parkin activity limits cytochrome c release. HeLa cells or HeLa cells expressing Parkin were treated and analysed Immunoblots are representative of three independent experiments. Ubiquitinated BAK indicated (arrow). Graph shows densitometric analysis of three independent experiments showing cytochrome c release (supernatant/supernatant+membrane) relative to 100 nM cBID as 100% release. Error bars represent mean +/- SD. 