A schematic diagram of the protein–ligand interactions in two distantly related proteins: (a) thymidylate synthase from S. aureus (PDB entry 4eaq) and (b) human thymidylate synthase (PDB entry 1e99). The ligands (blue bonds) in both are identical: 3′-azido-3′-deoxythymidine 5′-monophosphate. Equivalent protein residues in the two plots are circled in red and occupy the same positions in each plot: for example, Glu37 is equivalent to Phe42, Phe66 is equivalent to Phe72 and Tyr100 is equivalent to Phe105. Hydrogen bonds are depicted by green dotted lines and labelled with their length in Å, while hydrophobic interactions are represented by red arcs whose spokes radiate towards the ligand. The diagram was generated using LigPlot+ (Laskowski & Swindells, 2011).