Figure 2.
Auto-inhibition model of Chk1 regulation. A. Using the same color scheme as in Figure 1, in its inactive (unphosphorylated) state, the C-terminal domain physically interacts with the kinase domain, precluding it from phosphorylating substrates. B. This intramolecular interaction is blocked by S345 phosphorylation, opening the molecule to uncover the kinase domain.