6n6x

OXA-23 mutant F110A/M221A neutral pH form imipenem complex

spinqualitylabelsall models 6n6x, resolution 3.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6n6x is a 1 chain structure with sequence from Acinetobacter baumannii. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3.1Å Ligands: ID1, KCX, SO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q9L4P2_ACIBA Publication Abstract from PubMed Class D carbapenemases are enzymes of utmost clinical importance due to their ability to confer resistance to the last resort carbapenem antibiotics. We investigated the role of the conserved hydrophobic bridge in the carbapenemase activity of OXA-23, the major carbapenemase of the important pathogen, Acinetobacter baumannii We show that substitution of the bridge residue Phe110 affects resistance to meropenem and doripenem and has little effect on MICs of imipenem. The opposite effect was observed upon substitution of the other bridge residue, Met221. Complete disruption of the bridge by the F110A/M221A substitution resulted in a significant loss of affinity for doripenem and meropenem, and to a lesser extent, for imipenem, which is reflected in the reduced MICs of these antibiotics. In the wild-type OXA-23, the pyrrolidine ring of the meropenem tail forms a hydrophobic interaction with Phe110 of the bridge. Similar interactions would ensue with ring-containing doripenem but not with imipenem, which lacks this ring. Our structural studies showed that this interaction with the meropenem tail is missing in the F110A/M221A mutant. These data explain why disruption of the interaction between the enzyme and the carbapenem substrate impacts the affinity and MICs of meropenem and doripenem to a larger degree than those of imipenem. Our structures also show that the bridge directs the acylated carbapenem into a specific tautomeric conformation. However, it is not this conformation, but rather the stabilizing interaction between the tail of the antibiotic and the hydrophobic bridge that contributes to the carbapenemase activity of class D beta-lactamases. Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D beta-Lactamases.,Stewart NK, Smith CA, Antunes NT, Toth M, Vakulenko SB Antimicrob Agents Chemother. 2018 Dec 10. pii: AAC.02191-18. doi:, 10.1128/AAC.02191-18. PMID:30530607 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Beta-lactamase 3D structures

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