5IKQ

The Structure of Meclofenamic Acid Bound to Human Cyclooxygenase-2


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.41 Å
  • R-Value Free: 0.212 
  • R-Value Work: 0.171 
  • R-Value Observed: 0.173 

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Ligand Structure Quality Assessment 


This is version 2.1 of the entry. See complete history


Literature

Substrate-selective Inhibition of Cyclooxygeanse-2 by Fenamic Acid Derivatives Is Dependent on Peroxide Tone.

Orlando, B.J.Malkowski, M.G.

(2016) J Biol Chem 291: 15069-15081

  • DOI: https://doi.org/10.1074/jbc.M116.725713
  • Primary Citation of Related Structures:  
    5IKQ, 5IKR, 5IKT, 5IKV

  • PubMed Abstract: 

    Cyclooxygenase-2 (COX-2) catalyzes the oxygenation of arachidonic acid (AA) and endocannabinoid substrates, placing the enzyme at a unique junction between the eicosanoid and endocannabinoid signaling pathways. COX-2 is a sequence homodimer, but the enzyme displays half-of-site reactivity, such that only one monomer of the dimer is active at a given time. Certain rapid reversible, competitive nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to inhibit COX-2 in a substrate-selective manner, with the binding of inhibitor to a single monomer sufficient to inhibit the oxygenation of endocannabinoids but not arachidonic acid. The underlying mechanism responsible for substrate-selective inhibition has remained elusive. We utilized structural and biophysical methods to evaluate flufenamic acid, meclofenamic acid, mefenamic acid, and tolfenamic acid for their ability to act as substrate-selective inhibitors. Crystal structures of each drug in complex with human COX-2 revealed that the inhibitor binds within the cyclooxygenase channel in an inverted orientation, with the carboxylate group interacting with Tyr-385 and Ser-530 at the top of the channel. Tryptophan fluorescence quenching, continuous-wave electron spin resonance, and UV-visible spectroscopy demonstrate that flufenamic acid, mefenamic acid, and tolfenamic acid are substrate-selective inhibitors that bind rapidly to COX-2, quench tyrosyl radicals, and reduce higher oxidation states of the heme moiety. Substrate-selective inhibition was attenuated by the addition of the lipid peroxide 15-hydroperoxyeicosatertaenoic acid. Collectively, these studies implicate peroxide tone as an important mechanistic component of substrate-selective inhibition by flufenamic acid, mefenamic acid, and tolfenamic acid.


  • Organizational Affiliation

    From the Department of Structural Biology, The State University of New York at Buffalo and.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Prostaglandin G/H synthase 2
A, B
551Homo sapiensMutation(s): 0 
Gene Names: PTGS2COX2
EC: 1.14.99.1
UniProt & NIH Common Fund Data Resources
Find proteins for P35354 (Homo sapiens)
Explore P35354 
Go to UniProtKB:  P35354
PHAROS:  P35354
GTEx:  ENSG00000073756 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP35354
Glycosylation
Glycosylation Sites: 3Go to GlyGen: P35354-1
Sequence Annotations
Expand
  • Reference Sequence
Oligosaccharides

Help

Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
alpha-D-mannopyranose-(1-6)-alpha-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
C, D
4N-Glycosylation
Glycosylation Resources
GlyTouCan:  G04854NQ
GlyCosmos:  G04854NQ
GlyGen:  G04854NQ
Small Molecules
Ligands 5 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
COH
Query on COH

Download Ideal Coordinates CCD File 
I [auth A],
K [auth B]
PROTOPORPHYRIN IX CONTAINING CO
C34 H32 Co N4 O4
AQTFKGDWFRRIHR-RGGAHWMASA-L
JMS
Query on JMS

Download Ideal Coordinates CCD File 
F [auth A],
L [auth B]
2-[(2,6-dichloro-3-methyl-phenyl)amino]benzoic acid
C14 H11 Cl2 N O2
SBDNJUWAMKYJOX-UHFFFAOYSA-N
BOG
Query on BOG

Download Ideal Coordinates CCD File 
E [auth A]octyl beta-D-glucopyranoside
C14 H28 O6
HEGSGKPQLMEBJL-RKQHYHRCSA-N
NAG
Query on NAG

Download Ideal Coordinates CCD File 
G [auth A],
H [auth A],
M [auth B],
N [auth B]
2-acetamido-2-deoxy-beta-D-glucopyranose
C8 H15 N O6
OVRNDRQMDRJTHS-FMDGEEDCSA-N
AKR
Query on AKR

Download Ideal Coordinates CCD File 
J [auth A],
O [auth B],
P [auth B]
ACRYLIC ACID
C3 H4 O2
NIXOWILDQLNWCW-UHFFFAOYSA-N
Binding Affinity Annotations 
IDSourceBinding Affinity
JMS BindingDB:  5IKQ Ki: min: 200, max: 700 (nM) from 2 assay(s)
IC50: min: 40, max: 700 (nM) from 7 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.41 Å
  • R-Value Free: 0.212 
  • R-Value Work: 0.171 
  • R-Value Observed: 0.173 
  • Space Group: I 2 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 120.509α = 90
b = 134.053β = 90
c = 179.382γ = 90
Software Package:
Software NamePurpose
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling
PHASERphasing

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 General Medical Sciences (NIH/NIGMS)United StatesGM115386

Revision History  (Full details and data files)

  • Version 1.0: 2016-05-25
    Type: Initial release
  • Version 1.1: 2016-06-08
    Changes: Database references
  • Version 1.2: 2016-07-27
    Changes: Database references
  • Version 1.3: 2017-09-27
    Changes: Advisory, Author supporting evidence, Database references, Derived calculations
  • Version 1.4: 2019-12-25
    Changes: Author supporting evidence
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Derived calculations, Structure summary
  • Version 2.1: 2024-10-16
    Changes: Advisory, Data collection, Database references, Derived calculations, Structure summary