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Figure 5
Relative contribution of the electric potential (  ) and the H+ or Na+ concentration gradient (pH; pNa+) to the rate of ATP formation by three different ATP synthases. (A) Reconstituted chloroplast ATP synthase. K+/valinomycin diffusion potentials were applied in the absence ( ) or presence ( ) of pH = 206 mV. (B) Reconstituted E.coli ATP synthase. K+/valinomycin diffusion potentials were applied in the absence ( ) or presence ( ) of pH = 206 mV. (C) Reconstituted P.modestum ATP synthase. K+/valinomycin diffusion potentials were applied in the absence of pNa+ (5 mM NaCl present on either side of the membrane) ( ) or in the presence of pNa+ = 77 mV (outside 5 mM NaCl, inside 100 mM NaCl) ( ). ATP was determined as described in Materials and methods. Please note that ATP synthesis at = 0 was measured in the presence of valinomycin and 1 mM KCl on either side of the membrane in order to avoid interference with the generation of an electric potential through the movement of ions during ATP synthesis.
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