Figure 1.

Ion transport activity of GtCCR4 on ND7/23 cells recorded by a whole-cell patch clamp. (a) Representative photocurrents recorded at membrane potentials from −60 mV to +40 mV in 20 mV steps in standard solutions (See materials and methods). (b) Channel closing kinetics estimated by decay of photocurrents in standard solutions (N=8). Data represent the mean±SE. (c) I–V curves of stationary photocurrents with 110 mM (solid circle) or 0 mM (open circle) intercellular NaCl concentrations. The solution contained 110 mM NaCl, 2 mM CaCl₂, 2 mM MgCl₂, 5 mM KCl 10 mM EGTA-NaOH and 10 mM Hepes-NaOH (pH 7.2). A solution without Na⁺ contained 110 mM NMG-Cl, 2 mM CaCl₂, 2 mM MgCl₂, 5 mM KCl 10 mM EGTA-NMG and 10 mM Hepes-NMG (pH 7.2). Extracellular solution contained 140 mM NaCl, 2 mM CaCl₂, 2 mM MgCl₂, 2 mM KCl and Hepes-NaOH (pH 7.2). The photocurrent amplitudes were normalized at −80 mV as −1.0. Data represent the mean±SE. (d) I–V curves of stationary photocurrents with extracellular pH 5.0 (open circle) or pH 7.2 (solid circle) in the absence of NaCl. Extracellular solution contained 140 mM NMG-Cl, 2 mM CaCl₂, 2 mM MgCl₂ and Hepes-NMG (pH 7.2) or citric acid (pH 5.0). Intercellular solution contained 110 mM NMG-Cl, 2 mM CaCl₂, 2 mM MgCl₂, 5 mM KCl 10 mM EGTA-NMG and 10 mM Hepes-NMG (pH 7.2). The x- and y-axis represent the membrane potential (mV) and normalized current, respectively. The currents were first measured at pH_o 7.2 (solid circle), followed by change in solution to pH 5.0 (open circle) (N=3). The photocurrent amplitudes were normalized at −80 mV at pH_o 7.2 (solid circle) as −1.0. The dashed line was the theoretical curve.