Figure 3

Voltage dependence of eKR2 photocurrents at different intra- and extracellular ionic compositions. (a) Photocurrent traces of eKR2 at high H⁺ gradients (0 mV). Photocurrents from the same cell at symmetric pH_i 9.0 (left) and after the extracellular buffer was exchanged to pH_e 5.0 (right) to create a high H⁺ gradient; top: 110 mM symmetric [Na⁺]_i/e; bottom: 1 mM symmetric [Na⁺]_i/e. (b) Voltage dependence of the stationary photocurrents of eKR2 at 110 mM [Na⁺]_i, pH_i 7.2 and different extracellular pH_e values and [Na⁺]_e as indicated (normalized to the symmetric condition; LJP corrected; mean ± SEM, n = 6, 5, and 6). (c) Same experiment as in (b) but at 1 mM [Na⁺]_i, pH_i 7.2 (normalized to the symmetric condition; LJP corrected; mean ± SEM, n = 8, 11, 8, and 6). (d) Same experiment as in (b) but at 110 mM [Na⁺]_i, pH_i 9.0 (normalized to the symmetric condition; LJP corrected; mean ± SEM, n = 7, 7, and 7). (e) Same experiment as in (b) but at 1 mM [Na⁺]_i, pH_i 9.0 (normalized to the symmetric condition; LJP corrected; mean ± SEM, n = 6, 5, 6, and 6).