Crystallization of and preliminary X-ray diffraction data for TET-repressor and the TET-repressor-tetracycline complex.

The TET-repressor encoded by the transposon Tn10 has been crystallized along with the repressor-tetracycline complex. Both crystals belong to the space group P43212 (or P41212) with cell dimensions a = b = 74.3(1) A, c = 94.2(2) A and a = b = 73.3(1) A, c = 94.6(2) A for the free and complexed repressor, respectively. There is one molecule of molecular weight 23,000 per asymmetric unit, and the biologically active dimer therefore consists of two identically formed subunits which are related by a crystallographic 2-fold axis. This isomorphism of TET-repressor and its tetracycline complex suggests that only minor, subtle changes in structure trigger binding to or release of the operator. The crystals of the native protein permit X-ray data collection to 3.2 A and those of the complexed repressor to 2.8 A.