Figure 2.

Structure of an initiator caspase. (A) Caspase-2, being an initiator caspase, contains an N-terminal CARD, followed by a large subunit containing the active site (p19) and a small subunit (p12). The structure also contains a nuclear localization signal (NLS). (B) Diagram showing the structures of the zymogens for caspase 8, another initiator caspase, and caspase 3, an effector caspase. The amino-terminal prodomains are shown in light green, large subunits are in blue, and small subunits are shown in green. The prodomain of caspase 8 contains two DEDs. Other initiator caspases may have a CARD instead. The heterotetrameric enzyme (right) results from proteolytic activation, as described in the text. Adapted from [7,45].