Functional comparison of DmCNGA and T318P mutant. (A; left) Sample traces of single-channel recordings of DmCNGA and T318P mutant at −100 mV in cell-attached configuration. (Right) Histogram of single-channel current at −100 mV. (B) Normalized macroscopic currents of wild-type DmCNGA and T318P mutant as a function of [cGMP]_i measured in inside-out patches at −100 mV. Data are fitted to the Hill equation. The K_1/2 and n of DmCNGA are 16.4 ± 1.8 µM and 1.3, respectively. The K_1/2 and n of T318P mutant are 15.2 ± 2.1 µM and 1.2, respectively. (C) I-V curves of DmCNGA and T318P mutant measured from whole-cell recordings at different external (bath) Ca²⁺ concentrations. (D) Fraction of unblocked current (I/I_max) at −100 mV as a function of external Ca²⁺ concentration. Data are fitted into a Hill equation with, K_i of 229.5 ± 25 µM and n of 0.62 for DmCNGA and K_i of 13.7 ± 2.2 µM and n of 0.59 for T318P. All error bars are mean ± SEM from five measurements.