Binding modes of the inhibitors at the active site of E. coli MetAP. In the stereo views, only five conserved residues that coordinate with Mn(II) ions (D97, D108, H171, E204, E235) and two conserved histdines (H79, H178) are shown. The bound inhibitors are 4 (A), 5 (B), 6 (C), 7 (D), and 8 (E), respectively. The colour scheme is as follows: gray, carbon (protein residues); yellow, carbon (inhibitor); blue, nitrogen; red, oxygen; green, chlorine; and cyan, fluorine. Mn(II) ions are shown as green spheres. SigmaA-weighted Fobs-Fcalc standard omit maps (inhibitor and metal ions were not included in the model for the structure-factor calculation) are shown superimposed on the refined structures as blue meshes contoured at 3.5 standard deviations of the resulting electron density map.