1I5Q

CRYSTAL STRUCTURE OF THE E. COLI AMPC BETA-LACTAMASE MUTANT N152A COVALENTLY ACYLATED WITH THE INHIBITORY BETA-LACTAM, MOXALACTAM


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.83 Å
  • R-Value Free: 0.206 
  • R-Value Work: 0.168 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Inhibition of AmpC beta-lactamase through a destabilizing interaction in the active site.

Trehan, I.Beadle, B.M.Shoichet, B.K.

(2001) Biochemistry 40: 7992-7999


  • PubMed Abstract: 
  • Beta-lactamases hydrolyze beta-lactam antibiotics, including penicillins and cephalosporins; these enzymes are the most widespread resistance mechanism to these drugs and pose a growing threat to public health. beta-Lactams that contain a bulky 6(7)a ...

    Beta-lactamases hydrolyze beta-lactam antibiotics, including penicillins and cephalosporins; these enzymes are the most widespread resistance mechanism to these drugs and pose a growing threat to public health. beta-Lactams that contain a bulky 6(7)alpha substituent, such as imipenem and moxalactam, actually inhibit serine beta-lactamases and are widely used for this reason. Although mutant serine beta-lactamases have arisen that hydrolyze beta-lactamase resistant beta-lactams (e.g., ceftazidime) or avoid mechanism-based inhibitors (e.g., clavulanate), mutant serine beta-lactamases have not yet arisen in the clinic with imipenemase or moxalactamase activity. Structural and thermodynamic studies suggest that the 6(7)alpha substituents of these inhibitors form destabilizing contacts within the covalent adduct with the conserved Asn152 in class C beta-lactamases (Asn132 in class A beta-lactamases). This unfavorable interaction may be crucial to inhibition. To test this destabilization hypothesis, we replaced Asn152 with Ala in the class C beta-lactamase AmpC from Escherichia coli and examined the mutant enzyme's thermodynamic stability in complex with imipenem and moxalactam. Consistent with the hypothesis, the Asn152 --> Ala substitution relieved 0.44 and 1.10 kcal/mol of strain introduced by imipenem and moxalactam, respectively, relative to the wild-type complexes. However, the kinetic efficiency of AmpC N152A was reduced by 6300-fold relative to that of the wild-type enzyme. To further investigate the inhibitor's interaction with the mutant enzyme, the X-ray crystal structure of moxalactam in complex with N152A was determined to a resolution of 1.83 A. Moxalactam in the mutant complex is significantly displaced from its orientation in the wild-type complex; however, moxalactam does not adopt an orientation that would restore competence for hydrolysis. Although Asn152 forces beta-lactams with 6(7)alpha substituents out of a catalytically competent configuration, making them inhibitors, the residue is essential for orienting beta-lactam substrates and cannot simply be replaced with a much smaller residue to restore catalytic activity. Designing beta-lactam inhibitors that interact unfavorably with this conserved residue when in the covalent adduct merits further investigation.


    Organizational Affiliation

    Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, Northwestern University, 303 East Chicago Avenue, Chicago, Illinois 60611-3008, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
BETA-LACTAMASE
A, B
358Escherichia coli (strain K12)Mutation(s): 1 
Gene Names: ampC (ampA)
EC: 3.5.2.6
Find proteins for P00811 (Escherichia coli (strain K12))
Go to UniProtKB:  P00811
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MOX
Query on MOX

Download SDF File 
Download CCD File 
A, B
(2R)-2-[(1R)-1-{[(2S)-2-carboxy-2-(4-hydroxyphenyl)acetyl]amino}-1-methoxy-2-oxoethyl]-5-methylidene-5,6-dihydro-2H-1,3-oxazine-4-carboxylic acid
MOXALACTAM DERIVATIVE (open form)
C18 H18 N2 O9
GOYCBKVVHGALFQ-RZAIGCCYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.83 Å
  • R-Value Free: 0.206 
  • R-Value Work: 0.168 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 117.661α = 90.00
b = 77.267β = 116.75
c = 97.677γ = 90.00
Software Package:
Software NamePurpose
CNSphasing
CNSrefinement
SCALEPACKdata scaling
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-06-20
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2011-08-24
    Type: Non-polymer description