FIGURE 7.

A model showing caspase-6 undergoes a helix-strand transition upon substrate binding. Before substrate binding, caspase-6 continuously interconverts between the noncanonical (helical) conformation and the canonical strand conformation and fully transitions to the strand conformation upon substrate binding. This transition may be facilitated by the presence of a dynamic hydrophobic patch (light orange, inset view) that could also function as an exosite for substrate binding. After substrate cleavage and release, caspase-6 exists in a dynamic equilibrium between the helical and strand states.