title: Crystal structure of the nickel-responsive transcription factor NikR.
abstract: 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.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Schreiter
authors.forename: Michael D
authors.initials: MD
authors.lastname: Sintchak
authors.forename: Yayi
authors.initials: Y
authors.lastname: Guo
authors.forename: Peter T
authors.initials: PT
authors.lastname: Chivers
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Drennan
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C402409:NikR protein, E coli; D012097:Repressor Proteins; D009532:Nickel