Fig. 3

Active site of EcKPRS. The active site of EcKPRS (a) is composed of residues from two chains of the protein (one colored with green carbon atoms and the other colored with yellow carbon atoms; oxygen atoms are colored red and nitrogen atoms are colored blue). Interactions with the AMP substrate (AMP has been modeled in from a superposition of EcKPRS to the Burkholderia pseudomallei PRPP synthetase (3DAH); the AMP is colored with grey carbon atoms) are made with both chains. In the structure of EcKPRS, two globular regions of density, modeled as phosphates are observed bound in the R5P binding site (b). The AMP is shown in the same position as in (a) as a point of reference. The electron density shown is from a difference map, generated prior to adding the phosphates, and is contoured at 2.5 σ