Essential for the control of the cell cycle at the G2/M (mitosis) transition. Interacts with the CDC2 protein kinase to form MPF. G2/M cyclins accumulate steadily during G2 and are abruptly destroyed at mitosis. Maximally expressed before mitosis. The levels peak late in the G2 phase of the cell cycle and are at a minimum in G1 phase. Present with 300 molecules/cell in log phase SD medium. Belongs to the cyclin family. Cyclin AB subfamily.