Figure 2.

Similarities and differences in apoptotic machinery across evolution. Many of the core proteins of the apoptotic pathway are conserved in nematodes (C. elegans), fruit flies (D. melanogaster), and mammals, and these protein families share some functional similarities (which is noted by matching colors in the figure). As an example, Apaf-1, which forms the backbone of the caspase-9 activating apoptosome in response to cytochrome c, has a homolog, dApaf-1 (dArk), in the Drosophila pathway, which facilitates Dronc activation, although it does not appear to be activated by cytochrome c. In C. elegans, CED-4 also auto-oligomerizes to form a complex that enables activation of the CED-3 caspase. For a more complete description of each pathway, including highlights of similarities and differences between species, please see the text.