1QG6

CRYSTAL STRUCTURE OF E. COLI ENOYL ACYL CARRIER PROTEIN REDUCTASE IN COMPLEX WITH NAD AND TRICLOSAN


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.202 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Kinetic and structural characteristics of the inhibition of enoyl (acyl carrier protein) reductase by triclosan.

Ward, W.H.Holdgate, G.A.Rowsell, S.McLean, E.G.Pauptit, R.A.Clayton, E.Nichols, W.W.Colls, J.G.Minshull, C.A.Jude, D.A.Mistry, A.Timms, D.Camble, R.Hales, N.J.Britton, C.J.Taylor, I.W.

(1999) Biochemistry 38: 12514-12525

  • DOI: 10.1021/bi9907779
  • Primary Citation of Related Structures:  
    1QG6

  • PubMed Abstract: 
  • Triclosan is used widely as an antibacterial agent in dermatological products, mouthwashes, and toothpastes. Recent studies imply that antibacterial activity results from binding to enoyl (acyl carrier protein) reductase (EACPR, EC 1.3.1.9). We first recognized the ability of triclosan to inhibit EACPR from Escherichia coli in a high throughput screen where the enzyme and test compound were preincubated with NAD(+), which is a product of the reaction ...

    Triclosan is used widely as an antibacterial agent in dermatological products, mouthwashes, and toothpastes. Recent studies imply that antibacterial activity results from binding to enoyl (acyl carrier protein) reductase (EACPR, EC 1.3.1.9). We first recognized the ability of triclosan to inhibit EACPR from Escherichia coli in a high throughput screen where the enzyme and test compound were preincubated with NAD(+), which is a product of the reaction. The concentration of triclosan required for 50% inhibition approximates to 50% of the enzyme concentration, indicating that the free compound is depleted by binding to EACPR. With no preincubation or added NAD(+), the degree of inhibition by 150 nM triclosan increases gradually over several minutes. The onset of inhibition is more rapid when NAD(+) is added. Gel filtration and mass spectrometry show that inhibition by triclosan is reversible. Steady-state assays were designed to avoid depletion of free inhibitor and changes in the degree of inhibition. The results suggest that triclosan binds to E-NAD(+) complex, with a dissociation constant around 20-40 pM. Triclosan follows competitive kinetics with respect to NADH, giving an inhibition constant of 38 pM at zero NADH and saturating NAD(+). Uncompetitive kinetics are observed when NAD(+) is varied, giving an inhibition constant of 22 pM at saturating NAD(+). By following regain of catalytic activity after dilution of EACPR that had been preincubated with triclosan and NAD(+), the rate constant for dissociation of the inhibitor (k(off)) is measured as 1.9 x 10(-4) s(-1). The association rate constant (k(on)) is estimated as 2.6 x 10(7) s(-1) M(-1) by monitoring the onset of inhibition during assays started by addition of EACPR. As expected, the ratio k(off)/k(on) = 7.1 pM is similar to the inhibition constants from the steady-state studies. The crystal structure of E. coli EACPR in a complex with coenzyme and triclosan has been determined at 1.9 A resolution, showing that this compound binds in a similar site to the diazaborine inhibitors. The high affinity of triclosan appears to be due to structural similarity to a tightly bound intermediate in catalysis.


    Organizational Affiliation

    AstraZeneca, Mereside, Macclesfield, Cheshire, U.K. walter.ward@astrazeneca.com



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
PROTEIN (ENOYL-[ACYL-CARRIER PROTEIN] REDUCTASE)A, B, C, D261Escherichia coliMutation(s): 0 
Gene Names: fabI
EC: 1.3.1.9
UniProt
Find proteins for P0AEK4 (Escherichia coli (strain K12))
Explore P0AEK4 
Go to UniProtKB:  P0AEK4
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
TCLIC50:  5   nM  BindingDB
TCLIC50:  430   nM  BindingDB
TCLIC50:  900   nM  BindingDB
TCLKd:  0.02200000174343586   nM  Binding MOAD
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.90 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.202 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 74.16α = 90
b = 80.29β = 104.46
c = 82.75γ = 90
Software Package:
Software NamePurpose
AMoREphasing
X-PLORrefinement
MOSFLMdata reduction
CCP4data scaling

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1999-09-21
    Type: Initial release
  • Version 1.1: 2008-04-26
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance