Indicate whether each of the following phosphorylation events typically activates (A) or inactivates (I) the protein that is being phosphorylated. Your answer would be a four-letter string composed of letters A and I only, e.g. IIIA.
( ) Phosphorylation of Cdc25 by M-Cdk
( ) Phosphorylation of condensin subunits by M-Cdk
( ) Phosphorylation of kinesin-5 by Aurora-A
( ) Phosphorylation of Ndc80 subunits by Aurora-B

Question

Indicate whether each of the following phosphorylation events typically activates (A) or inactivates (I) the protein that is being phosphorylated. Your answer would be a four-letter string composed of letters A and I only, e.g. IIIA.
( )	Phosphorylation of Cdc25 by M-Cdk
( )	Phosphorylation of condensin subunits by M-Cdk
( )	Phosphorylation of kinesin-5 by Aurora-A
( )	Phosphorylation of Ndc80 subunits by Aurora-B

Quizplus · Accepted Answer

M-Cdk activates the Cdc25 phosphatase in a positive feedback loop. It also phosphorylates condensin subunits, stimulating DNA binding and supercoiling activity. Along with Aurora-A, it also phosphorylates kinesins such as kinesin-5, stimulating microtubule binding and motor activity. Without tension in the kinetochore, Aurora-B phosphorylates and inactivates components of Ndc80, lowering its affinity for microtubule plus ends.

Indicate Whether Each of the Following Phosphorylation Events Typically Activates