Figure 2.

Currents from coinjection of α_wtα_wt and ββ (A) or α_wtα_m and ββ (B) dimers activated by a range of concentrations of cAMP. The pulse protocol is as in Fig. 1. (C) Data are normalized dose–response relations at 60 mV from patches with channels from coinjection of α and β monomers (triangles), α_wtα_wt and ββ dimers (squares), or α_wtα_m and ββ dimers (circles) for activation of the channels by cAMP. Superimposed on the data are fits of the dimer data to Hill equations of the form in Fig. 1. The fitted values of K_1/2 are 9.2 μM and 25 μM, and of n are 1.3 and 1.4 for channels from α_wtα_wt and ββ and α_wtα_m and ββ coinjections, respectively, and I_max was set at unity. (D) Desensitization is shown for currents with successive brief depolarizations to 60 mV given every 1 s, in the presence of saturating cAMP, for channels from α_wtα_wt and ββ or α_wtα_m injections. The former desensitize, like channels from α+β monomers, but the latter do not, like channels from α monomers.