title: Potassium is critical for the Ni(II)-responsive DNA-binding activity of Escherichia coli NikR.
abstract: The Escherichia coli NikR transcription factor is a Ni(II)-dependent repressor that regulates the production of a nickel ion transporter. The X-ray crystal structure of the Ni(II)-NikR-DNA bound complex revealed a K(+)-binding site positioned at the interface of the metal- and DNA-binding domains, but the significance of the potassium was unclear. Mutation of one of the K(+) ligands impairs the affinity and specificity of DNA binding in the presence of either stoichiometric or excess Ni(II). Removal of K(+) abrogates Ni(II)-responsive DNA binding completely while the addition of K(+) restores this activity. Furthermore, the observed K(+) dependence can be relieved by replacing the K(+) ligand Asp34 with an arginine. These mutagenesis and cation exchange experiments reveal that K(+) is a critical structural component for the activation of Ni(II)-responsive DNA binding by NikR.
authors.affiliation: Department of Chemistry, University of Toronto, Ontario, Canada M5S 3H6.
authors.forename: Sheila C
authors.initials: SC
authors.lastname: Wang
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Li
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Deborah B
authors.initials: DB
authors.lastname: Zamble
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation; D009532:Nickel / Q000737:chemistry / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011485:Protein Binding; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C402409:NikR protein, E coli; D012097:Repressor Proteins; D009532:Nickel; D004247:DNA; D011188:Potassium