Wang, SC, Li, Y, Robinson, CV and Zamble, DB (2010) Potassium is critical for the Ni(II)-responsive DNA-binding activity of Escherichia coli NikR. J. Am. Chem. Soc. 132:1506-7
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.
Binding Sites; Crystallography, X-Ray; DNA/chemistry; DNA/metabolism; Escherichia coli/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Models, Molecular; Mutation; Nickel/chemistry; Nickel/metabolism; Potassium/metabolism; Protein Binding; Repressor Proteins/chemistry; Repressor Proteins/genetics; Repressor Proteins/metabolism
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