CRYSTALLIZATION AND PRELIMINARY-X-RAY ANALYSIS OF THE TET-REPRESSOR OPERATOR COMPLEX/

Three crystal forms of the repressor protein TetR class D in complex w ith the palindromic 17 bp operator sequence containing T overhangs on both sides were obtained by hanging-drop vapor-diffusion methods using PEG 4000 and PEG monomethylether 5000 as precipitants. Although the c rystallization conditions were very similar, up to three different cry stal forms were observed in the same drop. The space groups are monocl inic C2, P2(1) and hexagonal P6(1)22. The asymmetric units of the latt er two crystal forms contain one repressor-operator complex. The cryst al structures of these forms were solved by molecular replacement usin g the Tet-repressor molecule of the complex with tetracycline as a sea rch model.