Cloning, expression, purification, crystallization and initial crystallographic analysis of transcription elongation factors GreB from Escherichia coli and Gfh1 from Thermus thermophilus

The Escherichia coli gene encoding the transcription cleavage factor GreB and the Thermus thermophilus gene encoding the anti-GreA transcription factor Gfh1 were cloned and expressed and the purified proteins were crystallized by the sitting-drop vapor-diffusion technique. The GreB and Gfh1 crystals, which were improved by macroseeding, belong to space group P4₁2₁2 (or P4₃2₁2), with unit-cell parameters a = b = 148, c = 115.2 Å and a = b = 59.3, c = 218.9 Å, respectively. Complete diffraction data sets were collected for the GreB and Gfh1 crystals to 2.6 and 2.8 Å resolution, respectively. Crystals of the selenomethionine proteins were obtained by microseeding using the native protein crystals and diffract as well as the native ones. The structure determination of these proteins is now in progress.