Figure 1.

Cysteine substitutions in α9 can hinder Bak mitochondrial insertion, but only prior to apoptosis. (a) The Bak C terminus comprises a hydrophobic transmembrane domain and a basic C-segment. Positions of the four Bcl-2 homology (BH) domains and C-terminal transmembrane domain in Bak are shown, as is part of the human Bak sequence. (b) Bak mitochondrial localization is decreased by cysteine substitutions in α9, but membrane insertion is complete after activation by tBid. Untreated cells were fractionated into cytosol and membrane fractions, and the membrane fractions then extracted with sodium carbonate to detect peripherally attached and membrane-inserted populations. Where indicated, membrane fractions were pre-treated with tBid to activate Bak. Data are representative of three independent experiments