Figure 9.

Darlin⁻ cells have normal adenylyl cyclase activation in response to G protein activation. Adenylyl cyclase activity was measured in cell lysates under basal conditions or in the presence of 40 μM GTPγS and 1 μM cAMP at room temperature for 2 min. The unregulated intrinsic enzyme activity was measured by adding 5 mM MnSO₄. The G protein-mediated activation was as robust in the darlin-null cells as in either wild-type or nonrecombinant control cells. In addition, the levels of MnSO₄ activity were similar in each cell line, suggesting that they were expressing comparable levels of adenylate cyclase. Results are presented in picomoles per minute per milligrams protein and represent the average of experiments performed in duplicate.