The gene product of histidine kinase DR2244 (putative phoR) encoded by Deinococcus radiodurans has been suggested to be involved in the PhoR-PhoB two-component regulatory system. This two-component signalling system is activated upon phosphate starvation in several bacteria, including D. radiodurans. Single crystals were obtained from a recombinant preparation of the catalytic/ATP-binding (CA) domain of D. radiodurans PhoR (79-224) overexpressed in Escherichia coli. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 46.9, b = 81.8, c = 204.6 A. The crystals contained six molecules in the asymmetric unit. Diffraction data were collected to 2.4 A resolution on beamline ID23-2 of the European Synchrotron Radiation Facility.