Binding of hydrogen ions by ATP

Plot the average binding NHof hydrogen ions by ATP at 298.15 K and 0.25 M ionic strength as a function of pH. Show that plotting equation 1.3-13 yields the same result as plotting 1.3-7. 

Since it is possible to calculate the mole fractions of the various species of ATP at a specified pH, the average binding of hydrogen ions NH can be calculated by use of... 

Since equation 2.1-6 applies to each reactant, we expect that the change in the binding of hydrogen ions ffa in the hydrolysis of ATP to ADP will be given by... 

The ATPase complex of chloroplasts (H -ATPase, ATP-synthase) carries out synthesis (hydrolysis) of ATP coupled with transmembrane transport of hydrogen ions. This complex consists of a hydrophylic catalytic part called coupling factor CF, and a hydrophobic part, CFq, the function of which is to translocate protons towards CF. CFj can bind as many as six nucleotide molecules / /. After CF precipitation by ammonium sulfate with subsequent gel filtration, the enzyme retains about 1 mol of tightly bound nucleotides consisting mainly of ADP /2/. 

Fig. 3. Adenine-nucleotide bindingto the N-terminal domain, (a) Secondary structure cartoon (as in Fig. lc),with ADP (stickmodel) boundin the pocket formed by the helical face of the domain, (b) Detail of the ATP/ADP-binding site. The bound nucleotide is shown as a CPK-colored ball-and-stick model, and the many water molecules bound in the site are shown as red spheres. Hydrogen bonds are indicated by broken yellow rods, and the ligand interactions of the magnesium ion by broken blue rods.

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