Question

Explain the activation of Protein Kinase A (A Kinase or PKA)

A) PKA is activated when cAMP binds to its regulatory subunits, causing their dissociation from the catalytic subunits. The free catalytic subunits are then able to phosphorylate target proteins.
B) PKA is activated by direct binding of ATP to its catalytic subunits, leading to a conformational change that allows the kinase to phosphorylate target proteins.
C) PKA is activated by the binding of GTP to its regulatory subunits, promoting their interaction with the catalytic subunits. This complex can then phosphorylate target proteins.
D) PKA is activated by the binding of IP3 to its regulatory subunits, triggering the release of catalytic subunits that phosphorylate target proteins.

Answer 1

Protein Kinase A (PKA) is activated when cAMP binds to its regulatory subunits, causing dissociation from the catalytic subunits. The active subunits then phosphorylate target proteins, leading to changes in cellular processes.

Step-by-step explanation:

Protein Kinase A (PKA) is activated when cAMP binds to its regulatory subunits, causing their dissociation from the catalytic subunits. The free catalytic subunits are then able to phosphorylate target proteins. This process is an example of G-protein mediated signal transduction, where the activated G-protein activates adenylyl cyclase, which produces cAMP.

Once cAMP binds to PKA, a conformational change occurs, leading to dissociation of the inactive tetramer into two cAMP-bound inert subunits and two active PKA subunits. The active PKA subunits can then phosphorylate target proteins, leading to changes in cellular processes.

Phosphorylation by PKA alters the structural orientation of the target proteins, activating them. This activation can lead to various cellular responses, mediated by the activated molecules.