Structural basis for the inhibition of Polo-like kinase 1

Polo-like kinase 1 (PLK1) is a master regulator of mitosis and is considered a potential drug target for cancer therapy. PLK1 is characterized by an N-terminal kinase domain (KD) and a C-terminal Polo-box domain (PBD). The KD and PBD are mutually inhibited, but the molecular mechanisms of the autoinhibition remain unclear. Here we report the 2.3-Å crystal structure of the complex of the Danio rerio KD and PBD together with a PBD-binding motif of Drosophila melanogaster microtubule-associated protein 205 (Map205 PBM). The structure reveals that the PBD binds and rigidifies the hinge region of the KD in a distinct conformation from that of the phosphopeptide-bound PBD. This structure provides a framework for understanding the autoinhibitory mechanisms of PLK1 and also sheds light on the activation mechanisms of PLK1 by phosphorylation or phosphopeptide binding.