PROTON-PUMPING MECHANISM
Transitions between different protonation states during the photocycle
Transitions between protonation states during the steps of the photo-cycle. A transition between two protonation states, indicated by a red downward arrow, is assumed to occur via single proton transfer (green arrow ) consistent with the non-equilibrium accessibility rules. Transitions between conformational states are indicated by yellow arrows. Although the changes in protonation may, in many instances, be concomitant with transitions between the conformational states of the protein, the former are assumed to follow the latter, to facilitate the visualization of the cycle.
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