National Center for
3LRT: Crystal Structure Of The Phosphoribosyl Pyrophosphate (Prpp) Synthetase From Thermoplasma Volcanium In Complex With Adp
The structures of Thermoplasma volcanium phosphoribosyl pyrophosphate synthetase bound to ribose-5-phosphate and ATP analogs
J. Mol. Biol. (2011) 413 p.844-856
Phosphoribosyl pyrophosphate (PRPP) synthetase catalyzes the transfer of the pyrophosphate group from ATP to ribose-5-phosphate (R5P) yielding PRPP and AMP. PRPP is an essential metabolite that plays a central role in cellular metabolism. The enzyme from a thermophilic archaeon Thermoplasma volcanium (Tv) was expressed in Escherichia coli, crystallized, and its X-ray molecular structure was determined in a complex with its substrate R5P and with substrate analogs beta,gamma-methylene ATP and ADP in two monoclinic crystal forms, P2(1). The beta,gamma-methylene ATP- and the ADP-bound binary structures were determined from crystals grown from ammonium sulfate solutions; these crystals diffracted to 1.8 A and 1.5 A resolutions, respectively. Crystals of the ternary complex with ADP-Mg(2+) and R5P were grown from a polyethylene glycol solution in the absence of sulfate ions, and they diffracted to 1.8 A resolution; the unit cell is approximately double the size of the unit cell of the crystals grown in the presence of sulfate. The Tv PRPP synthetase adopts two conformations, open and closed, at different stages in the catalytic cycle. The binding of substrates, R5P and ATP, occurs with PRPP synthetase in the open conformation, whereas catalysis presumably takes place with PRPP synthetase in the closed conformation. The Tv PRPP synthetase forms a biological dimer in contrast to the tetrameric or hexameric quaternary structures of the Methanocaldococcus jannaschii and Bacillus subtilis PRPP synthetases, respectively.