1NKI: Crystal Structure Of The Fosfomycin Resistance Protein A (fosa) Containing Bound Phosphonoformate

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.
PDB ID: 1NKIDownload
MMDB ID: 25990
PDB Deposition Date: 2003/1/3
Updated in MMDB: 2016/12
Experimental Method:
x-ray diffraction
Resolution: 0.95  Å
Source Organism:
Similar Structures:
Biological Unit for 1NKI: dimeric; determined by author and by software (PISA)
Molecular Components in 1NKI
Label Count Molecule
Proteins (2 molecules)
Probable Fosfomycin Resistance Protein(Gene symbol: PA1129)
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB