Fig. 2.

Minimalist kinetic modeling of rotary and alternative mechanisms for ATP synthesis. (A) Synthesis cycles for the rotary and basic alternating-access mechanisms, which are (kinetically) distinguished by their orders of proton transport. (B) Other possible mechanisms based on proton transport order for a 3:1 H⁺:ATP stoichiometry. Note that conformational processes, such as rotation, are implicitly included in the binding and chemical processes shown, in a thermodynamically consistent way. Alternative stoichiometries as well as event orders (binding and reaction sequences) were also considered as described in the text and SI Appendix.