Angle determined by the loop L3 and the plane of the active site of NDM-1 (PDB 3SPU, green), and L3IMP (PDB 6C6I, cyan) and L3Pro (PDB 6CAC, yellow) mutants.337 Angles between Zn1, Cα of Ser69 and Cα of Gly63 are as follows: L3IMP, 68°; NDM-1, 88°; and L3Pro, 110°. L3IMP corresponds to NDM-1 in which the L3 loop (residues 57 to 68) was replaced by the one from IMP-1; L3Pro is a mutant of NDM-1 with a Pro inserted after Ala68.