Experimental Data Snapshot

  • Resolution: 0.95 Å
  • R-Value Free: 0.176 
  • R-Value Observed: 0.147 

Starting Model: experimental
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Phosphonoformate: a minimal transition state analogue inhibitor of the fosfomycin resistance protein, FosA.

Rigsby, R.E.Rife, C.L.Fillgrove, K.L.Newcomer, M.E.Armstrong, R.N.

(2004) Biochemistry 43: 13666-13673

  • DOI: https://doi.org/10.1021/bi048767h
  • Primary Citation of Related Structures:  
    1NKI, 1NNR

  • PubMed Abstract: 

    Fosfomycin [(1R,2S)-epoxypropylphosphonic acid] is a simple phosphonate found to have antibacterial activity against both Gram-positive and Gram-negative microorganisms. Early resistance to the clinical use of the antibiotic was linked to a plasmid-encoded resistance protein, FosA, that catalyzes the addition of glutathione to the oxirane ring, rendering the antibiotic inactive. Subsequent studies led to the discovery of a genomically encoded homologue in the pathogen Pseudomonas aeruginosa. The proteins are Mn(II)-dependent enzymes where the metal is proposed to act as a Lewis acid stabilizing the negative charge that develops on the oxirane oxygen in the transition state. Several simple phosphonates, including the antiviral compound phosphonoformate (K(i) = 0.4 +/- 0.1 microM, K(d) approximately 0.2 microM), are shown to be inhibitors of FosA. The crystal structure of FosA from P. aeruginosa with phosphonoformate bound in the active site has been determined at 0.95 A resolution and reveals that the inhibitor forms a five-coordinate complex with the Mn(II) center with a geometry similar to that proposed for the transition state of the reaction. Binding studies show that phosphonoformate has a near-diffusion-controlled on rate (k(on) approximately 10(7)-10(8) M(-1) s(-1)) and an off rate (k(off) = 5 s(-1)) that is slower than that for fosfomycin (k(off) = 30 s(-1)). Taken together, these data suggest that the FosA-catalyzed reaction has a very early transition state and phosphonoformate acts as a minimal transition state analogue inhibitor.

  • Organizational Affiliation

    Department of Chemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
probable fosfomycin resistance protein
A, B
135Pseudomonas aeruginosa PAO1Mutation(s): 0 
Find proteins for Q9I4K6 (Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1))
Explore Q9I4K6 
Go to UniProtKB:  Q9I4K6
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9I4K6
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 0.95 Å
  • R-Value Free: 0.176 
  • R-Value Observed: 0.147 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 54.982α = 90
b = 66.895β = 90
c = 76.723γ = 90
Software Package:
Software NamePurpose
SHELXmodel building
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-01-13
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Source and taxonomy, Version format compliance
  • Version 1.3: 2016-12-14
    Changes: Structure summary
  • Version 1.4: 2023-08-16
    Changes: Data collection, Database references, Derived calculations, Refinement description