Experimental Data Snapshot

  • Resolution: 2.28 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.165 
  • R-Value Observed: 0.165 

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X-ray structure of the Asn276Asp variant of the Escherichia coli TEM-1 beta-lactamase: direct observation of electrostatic modulation in resistance to inactivation by clavulanic acid.

Swaren, P.Golemi, D.Cabantous, S.Bulychev, A.Maveyraud, L.Mobashery, S.Samama, J.P.

(1999) Biochemistry 38: 9570-9576

  • DOI: https://doi.org/10.1021/bi990758z
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The clinical use of beta-lactam antibiotics combined with beta-lactamase inactivators, such as clavulanate, has resulted in selection of beta-lactamases that are insensitive to inactivation by these molecules. Therefore, therapeutic combinations of an enzyme inactivator and a penicillin are harmless for bacteria harboring such an enzyme. The TEM beta-lactamase variants are the most frequently encountered enzymes of this type, and presently, 20 variants are designated as inhibitor-resistant TEM ("IRT") enzymes. Three mutations appear to account for the phenotype of the majority of IRT enzymes, one of them being the Asn276Asp substitution. In this study, we have characterized the kinetic properties of the inhibition process of the wild-type TEM-1 beta-lactamase and of its Asn276Asp variant with the three clinically used inactivators, clavulanic acid (clavulanate), sulbactam, and tazobactam, and we report the X-ray structure for the mutant variant at 2.3 A resolution. The changes in kinetic parameters for the interactions of the inhibitors with the wild-type and the mutant enzymes were more pronounced for clavulanate, and relatively inconsequential for sulbactam and tazobactam. The structure of the Asn276Asp mutant enzyme revealed a significant movement of Asp276 and the formation of a salt bridge of its side chain with the guanidinium group of Arg244, the counterion of the inhibitor carboxylate. A water molecule critical for the inactivation chemistry by clavulanate, which is observed in the wild-type enzyme structure, is not present in the crystal structure of the mutant variant. Such structural changes favor the turnover process over the inactivation chemistry for clavulanate, with profound phenotypic consequences. The report herein represents the best studied example of inhibitor-resistant beta-lactamases.

  • Organizational Affiliation

    Groupe de Cristallographie Biologique, Institut de Pharmacologie et de Biologie Structurale du CNRS, Toulouse, France.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
BETA-LACTAMASE263Escherichia coliMutation(s): 3 
Find proteins for P62593 (Escherichia coli)
Explore P62593 
Go to UniProtKB:  P62593
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP62593
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.28 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.165 
  • R-Value Observed: 0.165 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 41.82α = 90
b = 60.36β = 90
c = 88.65γ = 90
Software Package:
Software NamePurpose
MOSFLMdata reduction
X-PLORmodel building
CCP4data scaling
ROTAVATAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1999-08-18
    Type: Initial release
  • Version 1.1: 2008-04-26
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-04
    Changes: Refinement description
  • Version 1.4: 2021-11-03
    Changes: Database references
  • Version 1.5: 2023-08-09
    Changes: Data collection, Refinement description