1WE4

Crystal Structure of Class A beta-Lactamase Toho-1 G238C mutant


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.7 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.183 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

An Engineered Disulfide Bond between Residues 69 and 238 in Extended-Spectrum beta-Lactamase Toho-1 Reduces Its Activity toward Third-Generation Cephalosporins

Shimizu-Ibuka, A.Matsuzawa, H.Sakai, H.

(2004) Biochemistry 43: 15737-15745

  • DOI: 10.1021/bi048488u

  • PubMed Abstract: 
  • Previous crystallographic structural analysis of extended-spectrum beta-lactamase Toho-1 predicted that the high flexibility of beta-strand B3, the region that contains a conserved KTG motif and forms one wall of the substrate-binding site, could be ...

    Previous crystallographic structural analysis of extended-spectrum beta-lactamase Toho-1 predicted that the high flexibility of beta-strand B3, the region that contains a conserved KTG motif and forms one wall of the substrate-binding site, could be one of the key features contributing to Toho-1 activity toward third-generation cephalosporins. To investigate whether this possible flexibility really affects the substrate profile of this enzyme, two Toho-1 mutants have been produced, G238C and G238C/G239in, in which the glycine residue at position 238 was replaced with a cysteine and an additional glycine residue was inserted. Our intent was to introduce a disulfide bond between the cysteine residues at positions 69 and 238, and thus to lock the position of beta-strand B3. The results of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) titration indicated formation of a new disulfide bridge in the G238C mutant, although disulfide bond formation was not confirmed in the G238C/G239in mutant. Kinetic analysis showed that the activity of the G238C mutant decreased drastically against third-generation cephalosporins, while its catalytic efficiency against penicillins and first-generation cephalosporins was almost identical to that of the wild-type enzyme. This result was consistent with the prediction that flexibility in beta-strand B3 was critical for activity against third-generation cephalosporins in Toho-1. Furthermore, we have determined the crystal structure of the G238C mutant enzyme to analyze the structural changes in detail. The structural model clearly shows the introduction of a new disulfide bridge and that there is no appreciable difference between the overall structures of the wild-type enzyme and the G238C mutant, although the introduced disulfide bond slightly influenced the positions of Ser237 on beta-strand B3 and Asn170 on the Omega loop. The results of our kinetic and structural analyses suggest that the flexibility of beta-strand B3, as well as the positions of Ser237 and the Omega loop, is critical for the substrate specificity expansion of Toho-1.


    Organizational Affiliation

    Department of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. aibuka@mail.ecc.u-tokyo.ac.jp




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Beta-lactamase Toho-1
A
262Escherichia coliGene Names: bla
EC: 3.5.2.6
Find proteins for Q47066 (Escherichia coli)
Go to UniProtKB:  Q47066
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.7 Å
  • R-Value Free: 0.222 
  • R-Value Work: 0.183 
  • Space Group: P 32 2 1
Unit Cell:
Length (Å)Angle (°)
a = 72.705α = 90.00
b = 72.705β = 90.00
c = 98.268γ = 120.00
Software Package:
Software NamePurpose
CCP4data scaling
CNSphasing
CNSrefinement
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2005-03-15
    Type: Initial release
  • Version 1.1: 2008-04-30
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance