Cooper5e_Ch17

In mammalian cells members of the bcl 2 family act at

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Unformatted text preview: s of the Bcl-2 family act at mitochondria, which play a central role in controlling programmed cell death ( Figure 17.8). When activated, Bax and Bak form oligomers in the mitochondrial outer membrane. Formation of these Bax or Bak oligomers leads to the release of cytochrome c f rom the mitochondrial intermembrane space, either by forming pores or by interacting with other mitochondrial outer membrane proteins. The release of cytochrome c from mitochondria then triggers caspase activation. In particular, the key initiator caspase in mammalian cells (caspase-9) is activated by forming a complex with Apaf-1 in the apoptosome. In mammals, formation of this complex also requires cytochrome c. Under normal conditions of cell survival, cytochrome c is localized to the mitochondrial intermembrane space (see Figure 11.10) while Apaf-1 and caspase-9 are found in the cytosol, so caspase-9 remains inactive. Activation of Bax or Bak results in the release of cytochrome c to the cytosol, where it binds to Apaf-1 and triggers apoptosome formation and caspase-9 activation. Caspases are also regulated...
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This note was uploaded on 08/25/2009 for the course BIO 315 taught by Professor Steiner during the Spring '08 term at Kentucky.

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