Fig. 2: Voltage-dependent activation of K464 mutants at zero and saturating [cAMP] (10 µM).
a Exemplary current traces for mHCN2 activation. Left panel: protocol and representative traces for measuring steady-state activation and activation kinetics at zero [cAMP], right panel: as left panel but at saturating [cAMP] (10 µM). b, e Steady-state activation for K464E and K464A at zero and saturating [cAMP] in comparison to mHCN2, respectively. Solid lines indicate the result of a Boltzmann fit (equation 1) (n = 5 to 9). c, f Activation kinetics at zero and saturating [cAMP] for K464E, K464A, and mHCN2 (n = 5 to 9). d Activation kinetics for mHCN2 and K464E plotted versus normalized command voltage (Vcommand/V1/2). g Deactivation kinetics at zero and saturating [cAMP] for K464E, K464A, and mHCN2 after −120 mV command voltage (n = 5 to 7). h Mean V1/2 values and cAMP-induced shift of ΔV1/2 for all constructs (n = 5 to 33). i Effective gating charge zδ for all constructs. In all panels open symbols represent cAMP-free, filled symbols saturating cAMP conditions (n = 5 to 33). h, i Asterixes indicate significant difference between the respective mutant data and mHCHN2 data under the same cAMP condition. In all box plots dotted center lines represent median, box limits represent standard deviation, whiskers represent minimum and maximum values, cirles represent individual recordings, squares represent mean.
