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Figure 2
(a) Superposition of magnesium-bound MenF with apo-MenF (PDB code 2eua ), illustrating the relative positions of the secondary-structural elements that define the active-site cleft of MenF in the presence and absence of magnesium. The MenF–Mg2+ complex is shown in blue; 2eua is shown in beige. The interaction of Arg283 with Arg406 is shown, along with the alternate conformation of Arg283 in apo-MenF. The loop containing Arg406 is poorly defined by electron density in the apo-MenF structure. (b) Superposition of the active sites of MenF with bound magnesium (shown with blue C atoms; this work) and without magnesium (PDB code 2eua ; shown in yellow), illustrating the differences in the conformations of key active-site residues in the presence and absence of magnesium. The side chain of Glu416 was not present in the 2eua structure. Water molecules coordinated to Mg2+ are shown as green spheres. (c) The remarkable conservation among active-site residues of chorismate-utilizing enzymes suggests factors beyond the first sphere of the active-site impact catalysis and influence product distribution. A superposition of MenF (blue C atoms), anthranilate synthase (PDB code 1i7q ; green C atoms) in complex with benzoate and pyruvate and SS (PDB code 2fn1 ; yellow C atoms) in complex with salicylate and pyruvate is shown. Water molecules from MenF are shown in green; Mg2+ ions are shown in blue. The water molecule adjacent to Lys190 is in position to attack a substrate at C2 upon activation. Sulfate ions are found in locations analogous to those of the substrate carboxylate group and the cleaved pyruvoyl group in other chorismate-utilizing enzymes.

Journal logoBIOLOGICAL
ISSN: 1399-0047
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