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Figure 3.
Location of the 2 anion-binding sites in PSII. (A) Composite
omit Fo-Fc map (blue) and anomalous map (red) of PSII with
Br^− substitution contoured at σ = 1.0 and 4.0, respectively,
superimposed on the structure of the Mn[4]Ca cluster and its
surrounding regions. The structure of PSII with
Br^−substitution was shown by the molecular replacement method
with the structure of the PDB code 2AXT as the search model.
Color codes for the residues are as follows: yellow, D1; green,
D2; orange, CP43; purple, Mn atoms. (B) Composite omit Fo-Fc map
(blue) and anomalous map (red) of I^−-substituted PSII
contoured at σ = 1.0 and 4.0, respectively, superimposed on the
structure of the Mn[4]Ca cluster and its surrounding regions.
The structure of PSII with I^− substitution was shown by the
molecular replacement method. The color codes for the residues
are the same as in A. (C) Location of Br[1] relative to the
proton exit channel proposed in (16, 27–29). The residues of
PsbO are drawn in blue, and the residues of other subunits are
in the same colors as in A. The directions of atoms from Cα to
Cβ in the residues are indicated by capsule-shaped objects.
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