6UNB

Crystal structure of CTX-M-14 in complex with temocillin

  • Classification: HYDROLASE
  • Organism(s): Escherichia coli
  • Expression System: Escherichia coli
  • Mutation(s): No 

  • Deposited: 2019-10-11 Released: 2019-10-30 
  • Deposition Author(s): Sacco, M., Chen, Y.
  • Funding Organization(s): National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.30 Å
  • R-Value Free: 0.167 
  • R-Value Work: 0.125 
  • R-Value Observed: 0.127 

Starting Model: experimental
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This is version 2.4 of the entry. See complete history


Literature

Influence of the alpha-Methoxy Group on the Reaction of Temocillin with Pseudomonas aeruginosa PBP3 and CTX-M-14 beta-Lactamase.

Sacco, M.D.Kroeck, K.G.Kemp, M.T.Zhang, X.Andrews, L.D.Chen, Y.

(2019) Antimicrob Agents Chemother 64

  • DOI: https://doi.org/10.1128/AAC.01473-19
  • Primary Citation of Related Structures:  
    6UN1, 6UN3, 6UNB

  • PubMed Abstract: 

    The prevalence of multidrug-resistant Pseudomonas aeruginosa has led to the reexamination of older "forgotten" drugs, such as temocillin, for their ability to combat resistant microbes. Temocillin is the 6-α-methoxy analogue of ticarcillin, a carboxypenicillin with well-characterized antipseudomonal properties. The α-methoxy modification confers resistance to serine β-lactamases, yet temocillin is ineffective against P. aeruginosa growth. The origins of temocillin's inferior antibacterial properties against P. aeruginosa have remained relatively unexplored. Here, we analyze the reaction kinetics, protein stability, and binding conformations of temocillin and ticarcillin with penicillin-binding protein 3 (PBP3), an essential PBP in P. aeruginosa We show that the 6-α-methoxy group perturbs the stability of the PBP3 acyl-enzyme, which manifests in an elevated off-rate constant ( k off ) in biochemical assays comparing temocillin with ticarcillin. Complex crystal structures with PBP3 reveal similar binding modes of the two drugs but with important differences. Most notably, the 6-α-methoxy group disrupts a high-quality hydrogen bond with a conserved residue important for ligand binding while also being inserted into a crowded active site, possibly destabilizing the active site and enabling water molecule from bulk solvent to access and cleave the acyl-enzyme bond. This hypothesis is supported by the observation that the acyl-enzyme complex of temocillin has reduced thermal stability compared with ticarcillin. Furthermore, we explore temocillin's mechanism of β-lactamase inhibition with a high-resolution complex structure of CTX-M-14 class A serine β-lactamase. The results suggest that the α-methoxy group prevents hydrolysis by locking the compound into an unexpected conformation that impedes access of the catalytic water to the acyl-enzyme adduct.


  • Organizational Affiliation

    Department of Molecular Medicine, University of South Florida, Tampa, Florida, USA.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Beta-lactamase
A, B
263Escherichia coliMutation(s): 0 
Gene Names: blaCTX-M-14
EC: 3.5.2.6
UniProt
Find proteins for Q9L5C7 (Escherichia coli)
Explore Q9L5C7 
Go to UniProtKB:  Q9L5C7
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9L5C7
Sequence Annotations
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  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
PCA
Query on PCA
A, B
L-PEPTIDE LINKINGC5 H7 N O3GLN
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.30 Å
  • R-Value Free: 0.167 
  • R-Value Work: 0.125 
  • R-Value Observed: 0.127 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 45.11α = 90
b = 106.46β = 101.92
c = 47.67γ = 90
Software Package:
Software NamePurpose
REFMACrefinement
PDB_EXTRACTdata extraction
MOSFLMdata reduction
SCALAdata scaling
MOLREPphasing

Structure Validation

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Ligand Structure Quality Assessment 


Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)United StatesR21 AI147654

Revision History  (Full details and data files)

  • Version 1.0: 2019-10-30
    Type: Initial release
  • Version 1.1: 2019-11-20
    Changes: Database references
  • Version 2.0: 2019-12-18
    Changes: Author supporting evidence, Polymer sequence
  • Version 2.1: 2019-12-25
    Changes: Database references
  • Version 2.2: 2020-01-01
    Changes: Database references
  • Version 2.3: 2023-10-11
    Changes: Data collection, Database references, Derived calculations, Refinement description, Structure summary
  • Version 2.4: 2024-10-16
    Changes: Structure summary