Crystal structure of the nickel-responsive transcription factor NikR.
Publication Type:Journal Article
Source:Nat Struct Biol, Volume 10, Issue 10, p.794-9 (2003)
Keywords:Amino Acid Sequence, Crystallography, X-Ray, Escherichia coli, Escherichia coli Proteins, Molecular Sequence Data, Nickel, Protein Structure, Tertiary, Repressor Proteins
<p>NikR is a metal-responsive transcription factor that controls nickel uptake in Escherichia coli by regulating expression of a nickel-specific ATP-binding cassette (ABC) transporter. We have determined the first two structures of NikR: the full-length apo repressor at a resolution of 2.3 A and the nickel-bound C-terminal regulatory domain at a resolution of 1.4 A. NikR is the only known metal-responsive member of the ribbon-helix-helix family of transcription factors, and its structure has a quaternary arrangement consisting of two dimeric DNA-binding domains separated by a tetrameric regulatory domain that binds nickel. The position of the C-terminal regulatory domain enforces a large spacing between the contacts that each NikR DNA-binding domain can make with the nik operator. The regulatory domain of NikR contains four nickel-binding sites at the tetramer interface, each exhibiting a novel square-planar coordination by three histidines and one cysteine side chain.</p>