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. 2011 Feb 15;10(4):598–603. doi: 10.4161/cc.10.4.14793

Figure 4.

Figure 4

PTPs regulate an early step in Bak activation. In healthy cells Bak is phosphorylated at Y108 an maintained in an inactive state by an as yet unidentified protein tyrosine kinase(s) (PTK). Apoptotic stimuli result in the activation of PTPs that dephosphorylate Bak at Y108, an obligatory step that then permits the recruitment of BH3-only proteins that bind to Bak causing a conformational change and exposure of Bak-BH3 helix, that inserts into the hydrophobic groove on another Bak molecule for dimerization. Bak dimers then assemble into higher order complexes leading to pore formation in the mitochondrial outer membrane and release of apoptotic factors such as cytochrome c.