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 space-group P3n12 with cell dimensions a = b = 54.4 A, c = 135.5 A, 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 space-group P3n12 with cell dimensions a = b = 108.07 A, c = 131.81 A, and gamma = 120.00 degrees. Both crystal forms diffract to at least 2.3 A at a synchrotron light source. Single-site cysteine mutations have been introduced to provide mercury-binding sites for multiple isomorphous replacement.