Cyclic AMP is an important second messenger. It forms, as shown, when the membrane enzyme adenylyl cyclase is activated (as indicated, by the alpha subunit of a G protein).
The cyclic AMP then goes on the activate specific proteins. Some ion channels, for example, are gated by cyclic AMP. But an especially important protein activated by cyclic AMP is protein kinase A, which goes on the phosphorylate certain cellular proteins. The scheme below shows how cyclic AMP activates protein kinase A.
QUESTION: What is the substrate for adenylyl cyclase?
QUESTION: What does a protein kinase do?
QUESTION: What is the source of the alpha subunit of a G protein in the above figure?
QUESTION: List the subunits which comprise protein kinase A.