Crystallization, X-ray studies, and site-directed cysteine mutagenesis of the DNA-binding domain of OmpR

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 P3(n)12 with cell dimensions a = b = 54.4 Angstrom, c = 135.5 Angstrom, and gamma = 120.00 degrees. 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 spacegroup P3(n)12 with cell dimensions a = b = 108.07 Angstrom, c = 131.81 Angstrom, and gamma = 120.00 degrees. Both crystal forms diffract to at least 2.3 Angstrom at a synchrotron light source. Single-site cysteine mutations have been introduced to provide mercury-binding sites for multiple isomorphous replacement.