DNA binding and DNA bending by the MelR transcription activator protein from Escherichia coli

Nucleic Acids Res. 1997 May 1;25(9):1685-93. doi: 10.1093/nar/25.9.1685.


The Escherichia coli melR gene encodes MelR protein which is a member of the AraC/XylS family of bacterial transcription activators. The function of MelR was investigated by making a targeted deletion in the melR gene of the Escherichia coli chromosome. MelR is a transcription activator essential for melibiose- dependent expression of the melAB operon which is needed for bacterial growth with melibiose as a carbon source. To investigate the interactions of MelR at the melAB promoter, both full length MelR and a shortened derivative, MelR173, containing the C-terminal DNA-binding domain, were purified as fusions to glutathione- S -transferase. Circular permutation studies show that both full-length MelR and MelR173 induce an apparent bend upon binding to target sites at the melAB promoter. Bound full-length MelR, but not MelR173, can oligomerise to form larger complexes that are likely to be involved in transcription activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Binding Sites
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Molecular Sequence Data
  • Nucleic Acid Conformation*
  • Promoter Regions, Genetic
  • Protein Binding
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / isolation & purification
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*


  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • MelR protein, E coli
  • Recombinant Fusion Proteins
  • Trans-Activators