Final answer:
The securin protein is cleaved by ubiquitin ligase, allowing the cell to proceed to anaphase.
Step-by-step explanation:
The correct answer is c) Ubiquitin ligase. Ubiquitin ligase is the enzyme that cleaves the securin protein, allowing the cell to proceed to anaphase. Proteasome is a structure that degrades proteins, but it does not directly cleave securin.
Securin is cleaved by the proteasome to allow the cell to proceed to anaphase. During the cell cycle, securin binds to and inhibits a protease called separase. Once the cell is ready for anaphase, securin is marked for destruction with ubiquitin, which is then recognized by the proteasome, leading to securin degradation.
During the cell cycle, the progression from metaphase to anaphase is regulated by the degradation of securin. Securin inhibits the separase enzyme, which cleaves the cohesin proteins holding sister chromatids together. When securin is cleaved by ubiquitin ligase, the separase enzyme becomes active, leading to the separation of sister chromatids.
Cyclin is a protein that regulates the activity of cyclin-dependent kinase (Cdk) during the cell cycle. Cyclin and Cdk are involved in various cell cycle checkpoints but are not directly responsible for cleaving securin.Kinase is an enzyme that phosphorylates other proteins, but it does not specifically cleave securin.