Polo Like Kinase 1 (PLK1)

Plk1 consists of 603 amino acids and is 66kDa. In addition to the N-terminus kinase domain, there are two conserved polo-box regions of 30 amino acids at the C-terminus.

Plk1 is an early trigger for G2/M transition. Plk1 supports the functional maturation of the centrosome in late G2/early prophase and establishment of the bipolar spindle. Plk1 phosphorylates and activates cdc25C, a phosphatase that dephosphorylates and activates the cyclinB/cdc2 complex. Plk phosphorylates and activates components of the APC. The APC, which is activated by Fizzy-Cdc20 family proteins, is a cell cycle ubiquitin-protein ligase (E3) that degrades mitotic cyclins, chromosomal proteins that maintain cohesion of sister chromatids, and anaphase inhibitors.