The polo-like Ser/Thr kinases (Plk1, Plk2/Snk, Plk3/Prk/Fnk, Plk4/Sak, and the inactive kinase Plk5) play various roles in cytokinesis and mitosis. At their C terminus, they contain a tandemly repeated polo-box domain (PBD) (in the case of Plk4, a tandem repeat of cryptic PBDs is found in the middle of the protein followed by a C-terminal single repeat), which appears to be involved in autoinhibition and in mediating the subcellular localization. The latter may be controlled via interactions between the polo-box domain and phospho-peptide motifs. The phosphopeptide binding site is formed at the interface between the two tandemly repeated PBDs. The PBDs of Plk4/Sak appear unique in participating in homodimer interactions, though it is not clear whether and how they interact with phosphopeptides [, , , , , ].This entry represents the second polo-box domain found in Plk1, Plk2 and Plk3.
