1. Heterodimeric Protein Kinases
Presented By: Becky Knight

2. What makes up a heterodimeric Protein Kinases?
Two different Subunits.
Cyclin subunit: regulatory subunit. Increases and decreases during cell cycle. Turns on kinase activity and they are degraded at certain points in cell cycle.
Cyclin-dependant Kinase (Cdk): Catalytic subunit. No activity unless associated with a cyclin.

3. There are different kinds of Cdks for each phase.
G1 Cdk complex
S-phase Cdk complex
Mitotic Cdk complex

4. G1 Cdk Complex Activated by the cell when it is ready to replicate.
Begins breakdown of S-phase inhibitor and prepares cell for s-phase.
Activates the enzymes that are required for gene encoding and DNA replication.

5. S-phase Cdk Complex Regulates initiation of DNA replication.
Ensures that the DNA is replicated only once.
It begins to reactivate the s-phase inhibitor.

6. Mitotic Cdk Complex Mitosis-promoting Factor (MPF)
Released during the S-phase and G2 phase once DNA is replicated.
Regulates mitosis by activating: the breakdown of nuclear membrane, chromosome condensation, mitotic apparatus assembly, and chromosome alignment.
Activates Anaphase-promoting Complex.

7. Anaphase-promoting Complex
Activated by MPF complex.
Causes the reverse of mitosis.
Allows for sister chromatid separation and segregation.
Ends mitosis.

8. Questions???