Avibactam binding pocket comparison. CTX-M-15 covalently bound to avibactam (shown as yellow sticks) is overlaid with various enzyme structures. Residue labels represent standard class A numbering. (a) ESBL and non-ESBL class A β-lactamases, where the five TEM enzymes are in various shades of cyan, SHV-1 is in blue and CTX-M-15 bound to avibactam is in grey. (b) Overlay of class A carbapenemases: KPC-2 (green), SME-1 (pink), NMC-A (orange) and GES-5 (blue). (c) Overlays of PER-1 (blue), PER-2 (cyan), SME-1 (magenta), BEL-1 (green) and OXY-1 (orange). (d) Overlay of representative GES enzymes containing Gly (GES-1, green), Ser (GES-5, orange) or Asn (GES-2) at position 170. For clarity, the backbone of the CTX-M-15 protein has been removed from panels (b)–(d).