Fig. 5: Helices D and E control cAMP affinity in HCN2.

a Representative current traces (recorded at −30, −90 and −130 mV) and mean activation curves of HCN2 FL (black), ΔDE (red) in control solution (full symbols) and with 1 µM cAMP in the pipette solution (empty symbols). Scale bar is 200 pA x 500 ms. Half-activation voltage (V_1/2) and inverse slope factor (k) values are reported in Supplementary Table 2 together with the details on statistical analysis. Data are shown as mean ± SEM. b ΔV_1/2 as a function of cAMP concentration for the constructs, color-coded as in panel a. Data fit to the Hill equation (solid lines) yielded half maximal effective concentration (K_1/2) values of 1.69 and 45.8 µM and Hill coefficients (nH) values of 1 and 1 for HCN2 FL and ΔDE constructs, respectively. Each data point is an average of n ≥ 3 experiments (the exact number is reported in the source data file). Data are shown as mean ± SEM. c Representative current traces (recorded at −30, −90 and −130 mV) and mean activation curves of HCN2 ΔE (green) and D671A (purple) in control solution (full symbols) and with 1 µM cAMP in the pipette solution (empty symbols). Scale bar is 200 pA x 500 ms. Half-activation voltage (V_1/2) and inverse slope factor (k) values are reported in Supplementary Table 2 together with the details on statistical analysis. Data are shown as mean ± SEM. d cAMP-induced shift in V_1/2 in constructs from panels a and c. Data are shown as mean ± SEM.