Range 
for extravesicular pH=8.05 4.0±0.3: for extravesicular pH=8.45 3.9±0.2 H+/ATP

Organism 
Spinach Spinacia oleracea 
Reference 
Turina, Paola, Dietrich Samoray, and Peter Gräber. "H+/ATP ratio of proton transportcoupled ATP synthesis and hydrolysis catalysed by CF0F1—liposomes." The EMBO journal 22.3 (2003): 418426. abstract & p.423 left column bottom paragraph & fig.5PubMed ID12554643

Method 
Reconstitution of the spinach chloroplast F0F1 ATP synthase on lipid vesicles. ATP synthesis is coupled to a luciferase assay. 
Comments 
Abstract:"The analysis of the [ATP]/([ADP][Pi]) ratio as a function of ?pH (eq) and of the transmembrane electrochemical potential difference, ?µ~H+ (eq), resulted in H+/ATP ratios of 3.9 ± 0.2 at pH 8.45 and 4.0 ± 0.3 at pH 8.05." p.423 left column bottom paragraph:"In Figure 5, [investigators] have plotted the data from Figures 3 (top) and 4 (top) according to equation 4, i.e. the energy contribution resulting from the stoichiometric ratio Q was plotted versus the electrochemical potential difference of protons ?µ~H+ (eq) (bottom scale) and ?pH (eq) (top scale). The values of the two series of experiments (pHout = 8.45 and pHout = 8.05) resulted in two straight lines. The linear regressions yielded slopes of 3.9 ± 0.2 and 4.0 ± 0.3 for pHout = 8.45 and pHout = 8.05, respectively, which, according to equation 4, represent the stoichiometric ratio H+/ATP = n. The yaxis intercepts give the standard Gibbs free energies ?Gp°' (see equation 4), with the values of 37 ± 2 and 36 ± 3 kJ/mol for pHout = 8.45 and pHout = 8.05, respectively." 
Entered by 
Avi Flamholz 
ID 
111495 