Cyclin B / Cdk1 kinase

Formation and contraction of the cytokinetic actomyosin ring is dependent on signals from the cell cycle machinery. During mitosis Cyclin B / CDK1 phosphorylates myosin light chain (MLC) and this prevents Myosin II from functioning. When CDK1 is inactivated at anaphase dephosphorylation of MLC allows myosin light chain kinase (MLCK) to phosphorylate MLC at Ser19. This allows myosin bundle formation at the cleavage furrow and constriction of the actomyosin ring.