Question

A calmodulin-regulated kinase (CaM-kinase) is involved in spatial learning and memory. This kinase is able to phosphorylate itself such that its kinase activity can become independent of changes in the intracellular concentration of Ca2+. What would be the effect on the activity of CaM-kinase if there were a mutation that reduced its interaction with the protein phosphatase responsible for inactivating the kinase? A. The kinase would stay active for longer after a transient increase in intracellular Ca2+concentration. B. The kinase would be further activated after intracellular Ca2+concentration has dropped. C. The kinase would be inactivated rapidly after Ca2+ levels have dropped. D. The kinase would remain associated with calmodulin after Ca2+ levels have dropped. E. There would be no changes in the CaM-kinase activity.

Answer 1

If there were a mutation reducing the interaction with the protein phosphatase responsible for inactivating the kinase, the effect on the activity of CaM-kinase would be that the kinase would stay active for longer after a transient increase in intracellular Ca2+ concentration (Option A).

Step-by-step explanation:

CaM-kinase activity is regulated by the binding of calmodulin and the phosphorylation state of the kinase itself. In normal conditions, an increase in intracellular Ca2+ concentration activates CaM-kinase by promoting its binding with calmodulin. The subsequent autophosphorylation further enhances its activity. The presence of a mutation that reduces interaction with the protein phosphatase responsible for dephosphorylation would lead to a decreased rate of dephosphorylation and inactivation.

As a result, the kinase would stay active for a more extended period, even after intracellular Ca2+ levels have dropped, causing a prolonged activation of CaM-kinase.

Option A is the answer.