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Complexation of the nickel and cobalt transcriptional regulator RcnR with DNA.

ABSTRACT: RcnR is a transcription factor that regulates the homeostasis of cobalt and nickel in bacterial cells. Escherichia coli RcnR was crystallized with DNA that encompasses the DNA-binding site. X-ray diffraction data were collected to 2.9?Å resolution. The crystal belonged to space group P6₁22 or P6₅22, with unit-cell parameters a = b = 73.59, c = 157.66?Å, ? = ? = 90, ? = 120°.

SUBMITTER: Li C

PROVIDER: S-EPMC6957110 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Complexation of the nickel and cobalt transcriptional regulator RcnR with DNA.

Li Chao C Vavra Joseph W JW Carr Carolyn E CE Huang Hsin Ting HT Maroney Michael J MJ Wilmot Carrie M CM

Acta crystallographica. Section F, Structural biology communications 20200101 Pt 1

RcnR is a transcription factor that regulates the homeostasis of cobalt and nickel in bacterial cells. Escherichia coli RcnR was crystallized with DNA that encompasses the DNA-binding site. X-ray diffraction data were collected to 2.9 Å resolution. The crystal belonged to space group P6<sub>1</sub>22 or P6<sub>5</sub>22, with unit-cell parameters a = b = 73.59, c = 157.66 Å, α = β = 90, γ = 120°. ...[more]

PMID: 31929183

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Project description:Escherichia coli RcnR (resistance to cobalt and nickel regulator, EcRcnR) is a metal-responsive repressor of the genes encoding the Ni(II) and Co(II) exporter proteins RcnAB by binding to PRcnAB. The DNA binding affinity is weakened when the cognate ions Ni(II) and Co(II) bind to EcRcnR in a six-coordinate site that features a (N/O)5S ligand donor-atom set in distinct sites: while both metal ions are bound by the N terminus, Cys35, and His64, Co(II) is additionally bound by His3. On the other hand, the noncognate Zn(II) and Cu(I) ions feature a lower coordination number, have a solvent-accessible binding site, and coordinate protein ligands that do not include the N-terminal amine. A molecular model of apo-EcRcnR suggested potential roles for Glu34 and Glu63 in binding Ni(II) and Co(II) to EcRcnR. The roles of Glu34 and Glu63 in metal binding, metal selectivity, and function were therefore investigated using a structure/function approach. X-ray absorption spectroscopy was used to assess the structural changes in the Ni(II), Co(II), and Zn(II) binding sites of Glu → Ala and Glu → Cys variants at both positions. The effect of these structural alterations on the regulation of PrcnA by EcRcnR in response to metal binding was explored using LacZ reporter assays. These combined studies indicate that while Glu63 is a ligand for both metal ions, Glu34 is a ligand for Co(II) but possibly not for Ni(II). The Glu34 variants affect the structure of the cognate metal sites, but they have no effect on the transcriptional response. In contrast, the Glu63 variants affect both the structure and transcriptional response, although they do not completely abolish the function of EcRcnR. The structure of the Zn(II) site is not significantly perturbed by any of the glutamic acid variations. The spectroscopic and functional data obtained on the mutants were used to calculate models of the metal-site structures of EcRcnR bound to Ni(II), Co(II), and Zn(II). The results are interpreted in terms of a switch mechanism, in which a subset of the metal-binding ligands is responsible for the allosteric response required for DNA release.

Dataset Information

Complexation of the nickel and cobalt transcriptional regulator RcnR with DNA.

Publications

Complexation of the nickel and cobalt transcriptional regulator RcnR with DNA.

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