FIGURE 7.

Model of caspase conformational states. Caspases exist in a conformational equilibrium between active and inactive states. The inflammatory caspase-1 resides primarily in the inactive conformation (“off” state), and binding to the active site selects for the active conformation (“on” state), which can serve as a template for another monomer to bind and form an active dimer. The executioner caspase, caspase-3, resides primarily in the active conformation; binding in the active site has little additional effect on this equilibrium and enzyme activity.