The gene encoding the unusual metal-ion-dependent epoxidase involved in fosfomycin biosynthesis, S. wedmorensis (S)-2-hydroxypropylphosphonic acid epoxidase, has been cloned and the protein expressed, purified and crystallized. Two crystal forms have been obtained, one of which diffracts to high resolution.
The oxirane (1R,2S)-1,2-epoxypropylphosphonic acid (fosfomycin) is a natural product antibiotic produced in Streptomyces wedmorensis by the metal-ion-dependent (S)-2-hydroxypropylphosphonic acid epoxidase. This epoxidase is highly unusual since it has no requirement for a haem prosthetic group. The gene encoding the enzyme, fom4, has been cloned and a highly efficient recombinant source of the enzyme established. Two different crystal forms, tetragonal and hexagonal, have been obtained. The hexagonal form displays symmetry consistent with space group P61/522 and unit-cell parameters a = 86.44, c = 221.56 Å, γ = 120°. The Matthews coefficient, V
M, of 2.7 Å3 Da−1 corresponds to two subunits, each of approximate weight 21.4 kDa, in the asymmetric unit with 55% solvent content. These crystals diffract to high resolution and experimental phases are being sought to determine the structure.