$23$

Ordering

$1$ point

The second messenger cyclic AMP $($cAMP$)$ is synthesized from ATP by the activity of the enzyme adenylyI cyclase. Cyclic AMP, in turn, activates protein kinase A $($PKA$),$ also called cAMP$-$dependent protein kinase, which is responsible for most of the effects of cAMP within the cell.

Determine the correct steps in the activation of PKA, and then place them in the correct order, starting after the adenylyl cyclase reaction.

$1$ cytosolic cAMP increases

$2$ two cAMP molecules bind to each regulatory PKA subunit

$3$ the free catalytic subunits interact with proteins to phosphorylate Ser and Thr residues

$4$ the regulatory subunits dissociate from the catalytic subunits