Nature Structural Biology10, 794 - 799 (2003)
Published online: 14 September 2003; | doi:10.1038/nsb985
Crystal structure of the nickel-responsive transcription factor NikR
Eric R Schreiter1, Michael D Sintchak1, Yayi Guo1, Peter T Chivers2, 3, Robert T Sauer2
& Catherine L Drennan1
1
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 USA.
2
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139 USA.
3
Present address: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Correspondence should be addressed to Catherine L Drennan cdrennan@mit.edu
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 Å and the nickel-bound C-terminal regulatory domain at a resolution of 1.4 Å. 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.
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