Crystallization and preliminary X-ray crystallographic study of leucyl-tRNA synthetase from the archaeon Pyrococcus horikoshii.

The leucyl-tRNA synthetase (LeuRS) from the archaeon Pyrococcus horikoshii was overexpressed in a C-terminally truncated form in Escherichia coli, purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate as a precipitant. The crystals belong to the rhombohedral space group R3, with unit-cell parameters a = b = 186.20, c = 91.43 A, alpha = beta = 90, gamma = 120 degrees. The asymmetric unit contains one molecule of LeuRS, with a corresponding crystal volume per protein weight of 3.2 A3 Da(-1) and a solvent content of 60.7%. A data set diffracting to 2.2 A resolution was collected from a single crystal at 100 K. Selenomethionine-substituted protein crystals were prepared in order to solve the structure by the SAD phasing method.