Medium temperature, 310 K, provides single crystals of orotate phosphoribosyltransferase from Thermus thermophilus

Crystallization of orotate phosphoribosyltransferase from a thermophilic organism, Thermus thermophilus, was achieved using the hanging-drop vapour-diffusion method coupled with a macroseeding starter. Small needle-like microcrystals were grown in a fresh protein solution in the presence of 2-methyl-2,4-pentanediol at 298 K or below. Although these normal temperature conditions caused stacking crystallization, an increase of temperature to 310K permitted crystal growth. This was because of increased enzyme solubility at the higher temperature. The crystal was found to belong to the monoclinic space group P2₁ with unit-cell parameters a = 44.4, b = 59.6, c = 67.8 Å and β = 98.3°.