Adaptations to hypoxia play an important role in Mycobacterium tuberculosis pathogenesis. Rv0324， which contains an HTH DNA-binding domain and a rhodanese domain， is one of the key transcription regulators in response to hypoxia. M. tuberculosis Rv1674c is a homologue of Rv0324. To understand the interdomain interaction and regulation of the HTH domain and the rhodanese domain， recombinant Rv1674c protein was purified and crystallized by the vapour-diffusion method. The crystals diffracted to 2.25 Å resolution. Preliminary diffraction analysis suggests that the crystals belonged to space group P3121 or P3221， with unit-cell parameters a = b = 67.8， c = 174.5 Å， α = β = 90， γ = 120°. The Matthews coefficient was calculated to be 2.44 Å  Da(-1)， assuming that the crystallographic asymmetric unit contains two protein molecules.