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Unformatted text preview: the key initiator caspase (caspase-9) is activated by binding to Apaf-1 in a multisubunit complex called the apoptosome (Figure 17.5). Formation of this complex in mammals also requires Cytochrome c
(initiator caspase) Pro-caspase-3 Apaf-1 Active caspase-3
Effector caspase Apoptosis FIGURE 17.5 Caspase activation The mammalian initiator caspase-9 is activated as a complex with Apaf-1 and cytochrome c in the apoptosome. Caspase-9 then
cleaves and activates effector caspases, such as caspase-3. This material cannot be copied, reproduced, manufactured, or disseminated in any
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© 2009 Sinauer Associates, Inc. UNCORRECTED PAGE PROOFS
CELL DEATH AND CELL RENEWAL cytochrome c, which is released from mitochondria by stimuli that trigger
apoptosis (discussed in the following section). Once activated in the apoptosome, caspase-9 cleaves and activates downstream effector caspases, such
as caspase-3 and caspase-7, eventually resulting in cell death. Central Regulators of Apopt...
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