Abstract
A C‐terminal fragment of the transcription factor OmpR has been crystallized using the sitting drop vapor‐diffusion method. Crystals belong to the trigonal spacegroup P3n12 with cell dimensions a = b = 54.4 Å, c = 135.5 Å, and γ = 120.00°. A second crystal form has been obtained by soaking this crystal form in a cryo‐buffer and flash‐cooling to 108 K in a cold nitrogen stream. Crystals belong to the trigonal space‐group P3n12 with cell dimensions a = b = 108.07 Å, c = 131.81Å, and γ = 120.00°. Both crystal forms diffract to at least 2.3 Å at a synchrotron light source. Single‐site cysteine mutations have been introduced to provide mercury‐binding sites for multiple isomorphous replacement.