Expression, purification, crystallization and preliminary X‐ray diffraction analysis of the transcriptional repressor SirR from Mycobacterium tuberculosis H37Rv
SirR, a metal‐dependent transcriptional repressor from Mycobacterium tuberculosis (Rv2788), was cloned in pQE30 expression vector with an N‐terminal His6 tag for heterologous overexpression in Escherichia coli M15 (pREP4) cells and purified to homogeneity using chromatographic procedures. The purified protein was crystallized using the sitting‐drop vapour‐diffusion technique. The crystals belonged to the tetragonal space group P41212/P43212, with unit‐cell parameters a = 105.21, b = 105.21, c = 144.85 Å. The X‐ray diffraction data were processed to a maximum resolution of 2.5 Å. The Matthews coefficient suggests the presence of two (V M = 4.01 Å3 Da−1) to four (V M = 2.0 Å3 Da−1) molecules in the asymmetric unit. Calculation of the self‐rotation function shows a crystallographic fourfold symmetry axis along the z axis (χ = 90°) and also a twofold symmetry axis around the z axis (χ = 180°).
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