Figure 4.

Active site of PfNurA. (A) 2F_O–F_C electron density map (1.2σ) showing dAMP, Mn²⁺ and the interacting residues. H-bonds and ion pairs are shown as dotted lines. (B) An active site cleft. An active site cleft with a Mn²⁺ ion (red sphere) and dAMP (blue stick). The C-terminal end of another PfNurA monomer (yellow) is directed toward the active site cleft of the PfNurA monomer. The three domains are colored as in Figure 2B. (C) 2F_O–F_C electron density map (1.5σ) of two Mn²⁺ ions. Active site residues and water molecules are shown. H-bonds and ion pairs are shown as dotted lines. (D) Nuclease activity analysis of the two active site mutant proteins. TP 424/423 or (E) TP 580/124 was used as the substrate. Assay conditions were the same as those used in Figure 1B.