Crystallization and preliminary X‐ray analysis of the CRP–cAMP–DNA (full length) complex

The Escherichia coli cyclic AMP receptor protein (CRP) is a well known transcription activator protein. In this study, CRP was overexpressed, purified and cocrystallized with cAMP and a 38 bp full‐length double‐stranded DNA fragment. The full‐length segment differed from the half‐site fragments used in previous crystallization experiments and is more similar to the environment in vivo . CRP–cAMP–DNA crystals were obtained and diffracted to 2.9 Å resolution. The crystals belonged to space group P 3 1 21, with unit‐cell parameters a = b = 76.03, c = 144.00 Å. The asymmetric unit was found to contain one protein molecule and half a 38 bp full‐length double‐stranded DNA fragment, with a Matthews coefficient of 2.62 Å 3 Da −1 and a solvent content of 53.14%.