A young post-doctoral fellow was assigned the task of investigating the mechanism by which epinephrine stimulates the activation of adenylate cyclase. The post-doctoral fellow developed an in vitro assay utilizing isolated liver cells, which when stimulated with epinephrine, increased the production of cAMP. He then showed that the cells were really unnecessary, because he could reproduce the effect with cell membranes. Thus when epinephrine was added to membranes isolated from liver cells, cAMP would form if ATP was also in the incubation medium. During the course of the experiments, the post-doc ran out of ATP and ordered a new batch. In the interest of scientific integrity (and because he was spending his boss’ money and not his own), he ordered the most highly purified ATP available (which cost plenty more than the usual ATP). Upon repeating his experiments with the isolated cell membranes, he could not reproduce his results, i.e., no cAMP would form, even though the experiment still worked with the intact cells.

Question

A. Explain the post-doc’s mysterious results in terms of our current understanding of the mechanism of G-protein participation in signal-response coupling.
B. Design a simple experiment to test your explanation.