Figure 4.

(A) Schematic diagram of how α_wtα_m and ββ dimer coinjections could produce channels with an arrangement of two α-subunits and two β-subunits (Left) or three α-subunits and one β-subunit (Right). (B) Dose–response data for activation by cAMP of channels from coinjection of α_wt and β monomers (circles), α_wtα_m and ββ dimers (triangles), and α_m and β monomers (squares). The solid lines are the Hill fits to the α_wt and β monomer data and the α_wtα_m and ββ dimer data. For α_wt and β monomers, K_1/2 = 7.7 μM and n = 1.5. For α_wtα_m and ββ dimers, K_1/2 = 22 μM and n = 1.4. For α_m and β monomers (Hill fit not shown for clarity), K_1/2 = 63 μM and n = 1.5. The dashed line on the left is the prediction (see Methods) for the α-α-β-β arrangement shown on the Left in A and is a Hill equation curve with K_1/2 = 63 μM and n = 1.5. The dotted line on the right is the prediction for the α-α-α-β arrangement shown on the right in (A), and is a Hill equation curve with K_1/2 = 178 μM and n = 1.5. The encircled arrangement is the one best supported by the data.