Figure 4
Pump-activity of CarO::YFP at various pHs and other ion concentrations.
Cells were illuminated by a 561 nm-laser. (a) Influence of external pH on pump-activity. The relative pump activity is shown, which was normalized to the pump current at pH 7.4 and 0 mV. pH of bath solution varied from pH 5 (black squares, 10 cells), to pH 7.4 (red circles, 25 cells) and pH 9 (blue triangles, 13 cells); intracellular pH was kept at 7.4. (b) Influence of internal pH on pump activity. Extracellular pH was maintained at pH 7.4. Mean area specific photocurrent at intracellular pH 9 (3 cells), 7.4 (8 cells) and 5 (10 cells), respectively. (c) Analysis of pump activity in absence of extracellular chloride or intracellular sodium. Mean area-specific pump current to membrane voltage relationship of CarO is given. Sodium chloride in standard solutions (red circles, 14 cells) was replaced either intracellularly by potassium chloride (black squares, 5 cells) or extracellularly by sodium sulfate (blue triangles, 7 cells), without any remarkable effect on pump activity.
