We have examined the binding of Mnt repressor to operator DNA in vitro and have determined how this binding affects the level of transcription from two nearby promoters, Pant and Pmnt. Mnt binds to a region of DNA that overlaps the startpoint of transcription of Pant and the -35 region of Pmnt. Mnt represses transcription in vitro from Pant and enhances transcription from Pmnt. Protection and interference experiments show that Mnt binds to a single, 17 base-pair operator site. The operator sequence and the protein-DNA contacts are symmetric. Mnt makes major groove contacts on both faces of the operator DNA. At pH 7.5, 200 mm-KCl, 22 °C, the Mnt tetramer binds operator with high affinity Kd = 2.2 × 10-11m and the protein-DNA complex is quite stable (t 1 2 = 48 min). Operator binding shows large dependencies on pH, salt concentration, and temperature.
All Science Journal Classification (ASJC) codes
- Structural Biology
- Molecular Biology