Steady-state I-V curves (−300 to +80 mV) of E166G and E166A in symmetrical 140 mM Cl⁻. (A) I-V curve of E166G constructed in the absence (control) and presence of two concentrations of the indicated fatty acids. The measured current was normalized to that obtained in the control condition at +80 mV. Notice that various fatty acids with different molecular lengths all punch through the pore of the E166G mutant. (B) I-V curves of E166A in the absence and presence of CPA. An example of the E166A recording in the presence of 1 mM CPA is shown on the right.