Figure 6
Determinants of proton selectivity in the outer pore. (a) Representative photocurrents of Chrimson outer pore mutants at different voltages and different extracellular solution of 110 mM NaCl and pHe 7.2 (left), 1 mM NaCl and pHe 7.2 (middle) and 110 mM NaCl and pHe 9.0 (right) with intracellular 110 mM NaCl pHi 7.2. (b) Photocurrent amplitudes at extracellular 1 mM NaCl pHe 7.2 and −60 mV normalized to symmetric standard conditions of 110 mM NaCl pHe 7.2 (dashed line) (mean ± SD; LJP corrected; compared to WT by a two sample t-test; WT: n = 8 cells; F135A: n = 5, p = 0.63; Y159A: n = 4, p = 0.24; E4’D: n = 6, p = 0.52; E4’H: n = 6, p = 0.74; E4’Q: n = 8, p = 0.025; E4’A: n = 5, p = 0.0001; E5’D: n = 7, p = 0.041; E5’Q: n = 6, p < 0.0001; E5’S: n = 6, p < 0.0001; E5’A: n = 6, p < 0.0001). (c) Photocurrent amplitudes at extracellular 110 mM NaCl pHe 9.0 and −60 mV normalized to symmetric standard conditions of 110 mM NaCl pHe 7.2 (dashed line) (mean ± SD; LJP corrected; compared to WT by a two sample t-test; WT: n = 10 cells, F135A: n = 11, p = 0.93; Y159A n = 6, p = 0.001; E4’D: n = 6, p = 0.013; E4’H: n = 5, p = 0.06; E4’Q: n = 7, p < 0.0001; E4’A: n = 8, p < 0.0001; E5’D: n = 6, p = 0.8; E5’Q: n = 7, p < 0.0001; E5’S: n = 6, p < 0.0001; E5’A: n = 9, p < 0.0001). (d) Peak photocurrent amplitudes (gray) and photocurrent amplitude after 500 ms illumination (black) in symmetric 110 mM NaCl and pHi/e 7.2 and −60 mV normalized to the cell capacitance (mean ± SD; WT n = 16 cells; F135A n = 18; Y159A n = 6; E4’D n = 10; E4’H n = 8; E4’Q n = 8; E4’A n = 11; E5’D n = 12; E5’Q n = 8; E5’A n = 11; E5’S n = 11).
