Caspase Activation Intrinsic Pathway Cytochrome c is released
from the mitochondria of pre-apoptotic cells and binds to Apaf-1
in the presence of dATP/ATP. The interaction results in a
conformational change in Apaf-1 allowing the molecules of Apaf-1
to associate with each other. This formation results in a wheel-
like structure that contains 7 molecules each of Apaf-1,
cytochrome c and ATP. Pro-Caspase-9 contains a caspase
recruitment domain (CARD) that is used to mediate specific
interactions with Apaf-1 CARD, which becomes exposed on the
apoptosome during assembly. Pro-Caspase-9 is autoactivated and
after cleavage, mature caspase-9 remains bound to the apoptosome
where it is able to activate executioner caspases such as
caspase-3 and caspase-7.