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Figure 3.
Figure 3. Comparison of the GTP-dependent and ATP-dependent
PEPCK structures. (a) Ribbon representation of the human enzyme
with metal ions and non-hydrolyzable GTP shown in ball-and-stick
form. (b) The E. coli enzyme with bound metal ions and ATP shown
in the same orientation to highlight the similarity of the fold.
(c) The active site of the human enzyme with bound
non-hydrolyzable GTP. The Mg and Mn ions are shown as purple
spheres and water molecules are shown as red spheres. (d)
Corresponding view of the active site of the E. coli enzyme
complexed with ATP taken from the Protein Data Bank, entry
1aq2[6]. A bound molecule of pyruvate marks the location of the
PEP site. The indicated torsion angle (O4'-C1'-N9-C4) is 57°
(syn) for bound ATP, versus 236° (anti) for the GTP bound to
the human enzyme. Atoms in the Figures are colored by type, with
C, N, O, S, and P atoms in green, dark blue, red, yellow, and
light blue, respectively.
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