Fig. 3

DrHCN4 and DrHCN4L can form a heterotetrametric channel. (A) Representative current traces of a mixture of DrHCN4 and DrHCN4L mRNA. The mixed mRNA concentrations were 1:1 (green) and 3:1 (light green). Membrane potential was varied from −30 mV to −130 mV in 10-mV decrements and held for 5 s at each potential. The inset shows the stimulation protocol. (B) Activation curves of the mixed channels of DrHCN4 and DrHCN4L. The mixed mRNA concentrations were 1:1 (green) and 3:1 (light green). Blue and red curves are the activation curves of DrHCN4 and DrHCN4L, respectively. The Boltzmann function fits the activation curves (n = 5). All data are from the same batch of oocytes. Therefore, the data sets of DrHCN4 and DrHCN4L are different from the datasets used in Figures 1, ,2.2. (C) Representative current traces of a dominant-negative mutant with or without wild-type DrHCN4 or DrHCN4L. From top to bottom: DrHCN4 mutant (DrHCN4AAA) only, DrHCN4 (wild-type) + DrHCN4AAA, DrHCN4L (wild-type) + DrHCN4AAA. Wild-type and mutant cRNAs were mixed in a 1:1 ratio with 5 ng each. (D) Averaged current amplitudes at −100 mV were plotted as bar graphs [n = 5 for each except DrHCN4AAA alone (n = 4)].