A, vaborbactam-bound PBP3 structure with ligand in ball-and-stick representation with cyan-colored carbon atoms. The ligand’s oxygen located in the oxyanion hole (a), the carboxyl (b), the amide (c), and the five-membered thiophene (d) are labeled. B, ceftazidime-bound PBP3 (PDBid 3PBO, [30]; ceftazidime is shown with green-colored carbon atoms). The PBP3 superimposition with the vaborbactam PBP3 structure resulted in a RMSD of 0.45 Å for 473 Cα atoms. In addition to the same moieties a-c as in A, also labeled are the five-membered aminothiazole ring (d), and ceftazidime’s 2-carboxypropan-2-yl group (e). C, cefoperazone-bound PBP3 (PDBid 5DF8, [42]; cefoperazone is shown with gold-colored carbon atoms). The PBP3 superimposition with the vaborbactam PBP3 structure resulted in a RMSD of 1.76 Å for 473 Cα atoms. Moieties, if present as in A, are labeled. D, meropenem-bound PBP3 (PDBid 3PBR, [30]; meropenem is shown with dark green-colored carbon atoms). The PBP3 superimposition with the vaborbactam PBP3 structure resulted in a RMSD of 0.78 Å for 473 Cα atoms. Moieties, if present as in A, are labeled. E, aztreonam-bound PBP3 (PDBid 3PBS, [30]; aztreonam is shown with pink-colored carbon atoms). The PBP3 superimposition with the vaborbactam PBP3 structure resulted in a RMSD of 0.66 Å for 473 Cα atoms. Moieties, if present as in B, are labeled with b now indicating the sulfo moiety. F, zidebactam-bound PBP3 (PDBid 7KIW, [18]; zidebactam is shown with teal-colored carbon atoms). Moieties, if present as in E, are labeled.