Kinases And zymogens Flashcards
What can kinases do
Change the activity of other proteins
What change when a conformational change occurs in a protein
Torsion angle changes
In a kinase, what is phosphorylated to activate it
The threonine residue or serine residue is phosphorylated
What enzyme activated an inactive CDK in a Cyclin/CDK complex
CDK-activating kinase- it phosphorylates the CDK
What are the two sites on a kinase
Active site- where the substrate binds
Regulatory site- where phosphorylation occurs
The regulatory site isn’t in the active site
Where does the CDK bind on this protein(CDK activating kinase). Also label the active site, atp and the regulatory site
How does the active site of CDKs open
Conformation: In the absence of a cyclin, the CDK exists in an inactive conformation. The active site is obstructed by the T-loop (also called the activation loop), which prevents substrate access and proper ATP binding.
T-loop: The T-loop is a flexible region of the CDK that can block the active site, thus inhibiting the kinase activity
When a cyclin binds to a CDK, it induces a conformational change in the CDK. Cyclins are regulatory proteins that control the activity of CDKs by binding to them.
T-loop Movement: The binding of a cyclin to the CDK causes the T-loop to move away from the active site. This movement is necessary to expose the catalytic residues and the ATP-binding site.
Active Conformation: The conformational change induced by cyclin binding aligns key residues within the CDK active site, facilitating substrate binding and catalysis.
For full activation, some CDKs require phosphorylation on a threonine residue within the T-loop by a CDK-activating kinase (CAK).
Phosphorylation Effect: Phosphorylation of the T-loop stabilizes the open conformation, ensuring the active site remains accessible for substrate binding and ATP binding, thereby fully activating the CDK.
