Crystallization and preliminary X-ray diffraction studies of Streptococcus pyogenes plasmid pSM19035-encoded ω transcriptional repressor

The transcriptional repressor, ω protein, from the Streptococcus pyogenes broad-host-range plasmid pSM19035 was crystallized at pH 7.5 and 8.5 by the vapour-diffusion method using PEG 4000 as precipitant. Two crystal forms were obtained; the first belongs to the tetragonal space group P4₁2₁2 or P4₃2₁2 and the second to the hexagonal space group P6₁ or P6₅. The crystals are most likely to contain one ω protein in the asymmetric unit, with V(m) values of 3.2 and 3.5 ų Da^-1, respectively. The crystals diffract X-rays to 2.4 and 2.9 Å resolution for the tetragonal and hexagonal systems, respectively.