Superposition of IMP-6 and IMP-1 metallo-β-lactamase. (A) Superposition of chains A, B, C and D of IMP-6, shown in green, split pea, lime and pale green, respectively. (B) Superposition of chains A, B, C and D of IMP-1, shown in cyan, marine, teal and pale cyan, respectively.
(C) Superposition of chain A of IMP-6, IMP-1 and IMP-1 (open conformation) (PDB ID 1DDK). IMP-6 and IMP-1 are coloured in green and cyan, respectively. Two zinc ions are represented as pink spheres. IMP-1 (PDB ID 1DDK) is coloured in magenta. (D) The structure-based sequence alignment of IMP-6 and IMP-1 with other structure-solved IMP-type metallo-β-lactamases using the structure of IMP-1 from this study. References for each sequence are as follows: IMP-1, S71932; IMP-2, AB182996; IMP-6, AB753460; IMP-13, AJ512502; and IMP-18, AY780674. The figure was produced using ESPript 3.0 program (http://espript.ibcp.fr) (49).