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Figure 3.
Figure 3. The Nucleotide Binding SiteResidues involved in
nucleotide binding and catalysis and elements of secondary
structure in the cleft between two P4 monomers (cyan and
purple). Nucleotides and selected residues of the active site
are drawn in a ball-and-stick representation. Residues are
labeled in black only in the first panel. The nucleotides are
color coded according to their conformation: AMPcPP inactive
“I” (orange), AMPcPP active “A” (red), product “P”
(blue), and ADP-Mg^2+ (yellow). The electron density for the
bound nucleotides and ions, calculated from the final Fourier
difference (2F[o] − F[c]), is shown in a beige surface
representation (1.0 σ). Mg^2+ ions are shown as pink balls,
while the anomalous Fourier difference map for the Mn^2+ ions is
shown as magenta chicken wire. The phosphates are anchored by
residues of the P loop (colored in red). The views are chosen to
be equivalent for each nucleotide binding site. The associated
cartoon representation shows the coordination of nucleotides to
selected residues of the catalytic sites and divalent cations.
Distances (in Å) are shown as dotted lines.
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