Details

Autor(en) / Beteiligte

• Phillips, Christine M
• Schreiter, Eric R
• Guo, Yayi
• Wang, Sheila C
• Zamble, Deborah B
• Drennanplus.Gif, Catherine L

Titel

Structural Basis of the Metal Specificity for Nickel Regulatory Protein NikR

Ist Teil von

• Biochemistry (Easton), 2008-01, Vol.47 (7), p.1938-1946

Erscheinungsjahr

2008

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• In the presence of excess nickel, Escherichia coli NikR regulates cellular nickel uptake by suppressing the transcription of the nik operon, which encodes the nickel uptake transporter, NikABCDE. Previously published in vitro studies have shown that NikR is capable of binding a range of divalent transition metal ions in addition to Ni super(2+), including Co super(2+), Cu super(2+), Zn super(2+), and Cd super(2+). To understand how the high- affinity nickel binding site of NikR is able to accommodate these other metal ions, and to improve our understanding of NikR's mechanism of binding to DNA, we have determined structures of the metal-binding domain (MBD) of NikR in the apo form and in complex with Cu super(2+) and Zn super(2+) ions and compared them with the previously published structures with Ni super(2+). We observe that Cu super(2+) ions bind in a manner very similar to that of Ni super(2+), with a square planar geometry but with longer bond lengths. Crystals grown in the presence of Zn super(2+) reveal a protein structure similar to that of apo MBD with a disordered alpha3 helix, but with two electron density peaks near the Ni super(2+) binding site corresponding to two Zn super(2+) ions. These structural findings along with biochemical data on NikR support a hypothesis that ordering of the alpha3 helix is important for repressor activation.