Figure 3. Crystal structures of Plk1 PBD in complex with PL-42 or PL-49.

(A) The crystal structure of the Plk1 PBD-PL-42 complex showed that the N-terminal moiety of PL-42 interacts with the pyrrolidine hydrophobic region. (B) The overlay of the two distinct crystal structures of the Plk1 PBD-PL-49 complex revealed that the N-terminal cyclohexyl moiety of PL-49 possesses the dual-binding ability and interacts with either the Tyr-rich hydrophobic channel or the pyrrolidine hydrophobic region. Note that since the N-terminal arm of PL-49 (gray backbone) that points to the Tyr-rich hydrophobic channel could not be localized in the density maps because of its high flexibility, we were not able to model the cyclohexylmethyl segment using PyMOL [19].