Figure 4 Comparisons of EcppnP with HppE and BacB(A ) The monomeric structure of Ec ppnP. (B ) Superposition of Ec ppnP with HppE (PDB code: 4J1X). The HppE is colored in cyan. The substrate or ligand of HppE is shown as the stick. The metal ion is shown as a sphere. (C ) Superposition ofEc ppnP with BacB (PDB code: 3H9A). The HppE is colored in pink. The substrate of BacB is shown as the stick. The metal ion is shown as a sphere. (D ) Potential substrate binding residues inEc ppnP are shown as the stick. (E ) Residues in HppE for substrate binding and catalytic reaction. The substrate is shown as a stick colored yellow. (F ) Residues in BacB for substrate binding and catalytic reaction. The substrate is shown as a stick colored yellow.