Final answer:
Cyclin, the regulatory component of MPF, has a stimulatory effect on MPF activity, playing a key role in promoting cell cycle progression and mitosis by regulating the interaction with cdk.
Step-by-step explanation:
The regulatory component of MPF, called cyclin, has a stimulatory effect on MPF activity and it plays a part in regulating interactions with its substrates. Cyclin, as a regulatory polypeptide, must bind to cyclin-dependent kinase (cdk) to form an active MPF, also known as Mitosis Promoting Factor. This binding is crucial because the kinase activity of MPF, which is necessary for the cell to enter mitosis, is dependent on the presence and concentration of cyclin. The levels of cyclin fluctuate during the cell cycle, increasing to allow MPF activation and cell cycle progression, and decreasing after mitosis when MPF activity is no longer needed. Cyclins are thus the main regulatory molecules driving the forward momentum of the cell cycle by promoting mitosis.
While cyclins provide positive regulation for cell cycle progression, various Cdk inhibitors play a contrasting role by blocking the full activation of Cdks until certain conditions within the cell are met. These negative regulators ensure that the cell does not proceed through the cycle in unfavourable conditions, providing a fine-tuning mechanism alongside cyclins.