NikR is a ribbon‐helix‐helix DNA‐binding protein

Abstract

Escherichia coli NikR, a repressor with homologs in other bacteria and archaea, was identified as a potential new member of the ribbon‐helix‐helix (β‐α‐α) family of transcription factors in profile based sequence searches and in structure prediction experiments. Biophysical and biochemical characterization of the N‐terminal domain of NikR show that it has many features expected of a β‐α‐α protein including α‐helical content, dimeric solution form, concentration dependent thermal stability, and ability to bind DNA in sequence‐specific manner. Mutation of a residue predicted to be important for DNA‐binding reduces operator affinity but does not affect the secondary structure or stability of the protein.