Cytochrome c (m.w. 12,500) is an electron transport protein from mitochondria. It is released from mitochondria to cytoplasm during the early stages of apoptosis, prior to caspase activation, DNA fragmentation, and loss of membrane potential. The cytoplasmic cytochrome c is associated with Apaf-1 and caspase-9 to activate caspase-3 and other caspases