Crystallization and preliminary X-ray diffraction study of the farnesyl diphosphate synthase from Trypanosoma brucei.

Farnesyl diphosphate synthase (FPPS) catalyses the formation of farnesyl diphosphate from dimethylallyl diphosphate and isopentenyl diphosphate and is an RNAi-validated drug target in Trypanosoma brucei, the causative agent of African sleeping sickness. A T. brucei FPPS (390 amino acids) has been expressed in Escherichia coli and the recombinant protein has been crystallized in the absence and presence of the bisphosphonate inhibitor minodronate. Diffraction data were collected at 100 K using synchrotron radiation from both crystal types. Crystals obtained in the absence of minodronate belong to space group I222, with unit-cell parameters a = 61.43, b = 118.12, c = 120.04 A, while crystals grown in the presence of minodronate belong to space group C2, with unit-cell parameters a = 131.98, b = 118.10, c = 63.25 A, beta = 112.48 degrees. An initial model of the drug-free protein has been built using a homology model with the molecular-replacement method and refined to 3.3 A resolution. It shows mostly helical structure and resembles the structure of avian farnesyl diphosphate synthase, but with the addition of two loop regions.