Fig. 2

Ion selectivity of SsTRIC channel. a and b Representative recordings and current-voltage relationships of the wild-type SsTRIC measured under bi-ionic condition of 210 mM KCl (pipette) and 210 mM NaCl (bath). The I/V curve of wild-type SsTRIC measured under symmetrical 210 mM KCl (red) is included for comparison. The reversal potential (4.84 ± 0.86 mV for bi-ionic condition and −0.02 ± 0.63 mV for symmetrical condition) is derived by linear fitting of the I/V relationship data. The error bars indicate the standard errors of mean values (SEM, number of patches/n = 5 for bi-ionic condition, and n = 8 or 9 for symmetrical condition as shown in Fig. 1c). c, d, and e Representative recordings and current-voltage relationships of the wild-type SsTRIC (dark) and F104 A mutant (blue) measured under bi-ionic condition of 210 mM KCl (pipette)/210 mM KCl + 75 mM CaCl₂ (bath). The reversal potential is at 0.04 ± 0.09 mV (mean ± SEM, n = 4 except that n = 3 for the data point at −20 mV) for the wild type and 0.11 ± 1.77 mV (mean ± SEM, n = 5) for the F104A mutant. f and g Representative recordings and current-voltage relationships of the wild-type SsTRIC measured under bi-ionic condition of 210 mM KCl (pipette)/210 mM KCl + 75 mM MgCl₂ (bath). The reversal potential is at −0.04 ± 0.69 mV (mean ± SEM, n = 3). h and i Representative recordings and current-voltage relationships of F104A mutant measured under bi-ionic condition of 210 mM KCl (pipette)/210 mM NaCl (bath). For comparison, the I/V curve of wild-type tSsTRIC under the same condition is included i The reversal potential is at 1.92 ± 0.93 mV (mean ± SEM, n = 5 except that n = 3 for −20 mV and n = 4 for 40 mV) for F104A mutant or 4.84 ± 0.86 mV (mean ± SEM, n = 5) for the wild type. See Additional file 11 for the supporting data values