3JYI

Structural and biochemical evidence that a TEM-1 {beta}-lactamase Asn170Gly active site mutant acts via substrate-assisted catalysis


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.70 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.230 
  • R-Value Observed: 0.231 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history


Literature

Structural and biochemical evidence that a TEM-1 beta-lactamase N170G active site mutant acts via substrate-assisted catalysis

Brown, N.G.Shanker, S.Prasad, B.V.Palzkill, T.

(2009) J Biol Chem 284: 33703-33712

  • DOI: 10.1074/jbc.M109.053819
  • Structures With Same Primary Citation

  • PubMed Abstract: 
  • TEM-1 beta-lactamase is the most common plasmid-encoded beta-lactamase in Gram-negative bacteria and is a model class A enzyme. The active site of class A beta-lactamases share several conserved residues including Ser(70), Glu(166), and Asn(170) that ...

    TEM-1 beta-lactamase is the most common plasmid-encoded beta-lactamase in Gram-negative bacteria and is a model class A enzyme. The active site of class A beta-lactamases share several conserved residues including Ser(70), Glu(166), and Asn(170) that coordinate a hydrolytic water involved in deacylation. Unlike Ser(70) and Glu(166), the functional significance of residue Asn(170) is not well understood even though it forms hydrogen bonds with both Glu(166) and the hydrolytic water. The goal of this study was to examine the importance of Asn(170) for catalysis and substrate specificity of beta-lactam antibiotic hydrolysis. The codon for position 170 was randomized to create a library containing all 20 possible amino acids. The random library was introduced into Escherichia coli, and functional clones were selected on agar plates containing ampicillin. DNA sequencing of the functional clones revealed that only asparagine (wild type) and glycine at this position are consistent with wild-type function. The determination of kinetic parameters for several substrates revealed that the N170G mutant is very efficient at hydrolyzing substrates that contain a primary amine in the antibiotic R-group that would be close to the Asn(170) side chain in the acyl-intermediate. In addition, the x-ray structure of the N170G enzyme indicated that the position of an active site water important for deacylation is altered compared with the wild-type enzyme. Taken together, the results suggest the N170G TEM-1 enzyme hydrolyzes ampicillin efficiently because of substrate-assisted catalysis where the primary amine of the ampicillin R-group positions the hydrolytic water and allows for efficient deacylation.


    Organizational Affiliation

    Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.



Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-lactamase TEMA, B, C, D, E, F263Escherichia coliMutation(s): 1 
Gene Names: blablaT-3blaT-4blaT-5blaT-6TEM-1
EC: 3.5.2.6
Find proteins for P62593 (Escherichia coli)
Explore P62593 
Go to UniProtKB:  P62593
Protein Feature View
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  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
EPE
Query on EPE

Download CCD File 
A, B, C, D, E, F
4-(2-HYDROXYETHYL)-1-PIPERAZINE ETHANESULFONIC ACID
C8 H18 N2 O4 S
JKMHFZQWWAIEOD-UHFFFAOYSA-N
 Ligand Interaction
PO4
Query on PO4

Download CCD File 
A, B, C, E
PHOSPHATE ION
O4 P
NBIIXXVUZAFLBC-UHFFFAOYSA-K
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.70 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.230 
  • R-Value Observed: 0.231 
  • Space Group: P 43 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 88.099α = 90
b = 88.099β = 90
c = 500.352γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
PHASERphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2009-10-06
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance