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Figure 2.
Fig. 2. Structural details of the cap-binding site and ligand
complexes in the citrate (a–c) and MPD (d–f) crystal forms.
2F[o] − F[c] maps contoured at 1.8σ are shown for the apo (a
and d) and the bound GTP ligand (b and e) structures. Composite
2500K simulated-anneal omit maps are shown for the nonmethylated
GpppA cap analog in the citrate crystal form (c) and for the N7
methylated GpppA cap analog in the MPD crystal form (f). The
view in panel (c) is from the top of the GpppA binding site to
show the stacking interactions involving Phe24 and the guanosine
and adenosine from the cap analog. “W” denotes the bridging
water molecule. Residues described in the text are labeled in
(a) and (e).
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