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Figure 5.
Figure 5. Molecular Structure of the Chloride Ion Binding
Site
(A) Anomalous difference electron density map at 1.96
Å resolution for the GluR5 ligand binding core bromide
complex contoured at 6 σ (purple). The Br^− ion sits on the
molecular 2-fold between two subunits, colored red and blue
respectively, for which helices J and D are labeled. Side chains
that form salt bridges at the base and top of the anion binding
site are drawn in stick configuration.
(B) Sigma A-weighted
mF[o] − DF[c] electron density map at 2.11 Å resolution
for the GluR5 ligand binding core sulfate complex contoured at 3
σ (blue); sulfate was omitted from the F[c] calculation. Note
the altered conformation of Arg760 and the associated switch of
salt bridges from intermolecular to intramolecular contacts.
(C) Stereo view of the GluR5 chloride complex rotated by
90° from the view in (A) with a sigma A-weighted mF[o] −
DF[c] electron density map at 1.74 Å resolution contoured
at 5 σ for the Cl^− ion (green), side chains (gray), and
water molecules (blue); atoms drawn in stick configuration were
omitted from the F[c] calculation.
(D) Molecular surface
for domain 1 of the ligand binding core for one subunit in a
GluR5 dimer assembly colored by surface curvature (concave
green); the view is face-on to the anion binding site.
(E)
Electrostatic surface potential map for the GluR5 anion binding
site calculated with Cl^− removed from its binding site; the
view is the same orientation as in (D).
(F) Amino acid
sequence alignment and Cα movements (in Å) for the GluR5
and GluR2[flop] dimer crystal structures relative to the crystal
structure of the R/G site unedited GluR2[flip]. AMPA receptor
dimer structure.
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