FIGURE 3.

Relationship of the Cl⁻ pump activity of pHR to light intensity (A) and membrane potential (B). The photoinduced currents in the presence of 100 mM Cl⁻ were determined at steady state in pHR-expressing oocytes at different light intensities. The light intensity was measured with a photometer and expressed as percentage of maximal light intensity. (A) The dependence of photoinduced current at −50 mV on light intensity. (B) The dependence of photoinduced current on membrane potential at different light intensities. The V_R was estimated from the x-intercepts by the extrapolation of the lines describing the I-V relationship. The reversal potentials remained unchanged irrespective of the light intensity. The inset in B represents the dependence of V_R on light intensity. Data represent mean ± SE (n = 7–10).