Active site of CTX-M-15 Clavulanic acid-enzyme complex. (a) Electron density map of CTX-M-15 active site bound to clavulanic acid shown in yellow. 2Fo-Fc map (contoured at 1.0 sigma) is shown in grey which was built by UCSF Chimera v1.13.1 (San Francisco, CA, USA). Residues around the binding pocket of the clavulanic acid-CTX-M-15 crystal structure are depicted as cream, red, blue sticks. (b) 2D structure of clavulanic acid (orange) in the binding pocket of CTX-M-15. All residues have been shown, hydrogen bonds are drawn using dashed lines. The residues that interacted with clavulanic acid are in dark black, residues without interaction are shown in gray. The figure was built by the MarvinSketch v.17.28.0. (Budapest, Hungary).