Figure 9.

Proton exit channel suggested by the hydrated DFT QM/MM structural models, including a network of hydrogen bonds extended from substrate water molecules ‘s’ (slow) and ‘f’ (fast), via CP43-R357, to the first residue (D1-D61) leading to the lumenal side of the membrane (Sproviero et al. 2006d). Proton translocation events are indicated by blue and white arrows; the O=O bond formation event is indicated by a red arrow, as promoted by water exchange from Ca²⁺. Amino acid residues labeled with one-letter symbols correspond to the D1 protein subunit. Copyright 2006 American Chemical Society.