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Propriétés de métallation et de liaison à l'ADN de NikR d'Escherichia coli et de NikR et FUR d'Helicobacter pylori

Abstract : The transcription factors NikR and FUR are involved in the nickel and iron homeostasis. Comparative studies of metal and DNA binding properties of E.coli (Ec) and H.pylori (Hp) NikR are reported.
EcNikR, a tetramer, binds up to 8 nickels per monomer. EcNikR contains two types of metal sites. The first one, a high affinity site, binds one nickel with a submicromolar dissociation constant. Other sites with a lower affinity are involved in a Ni(II) and pH dependant aggregation process. HpNikR and EcNikR share common metal binding properties such as the binding of different transition metals (Cu(II), Ni(II), Co(II)) in their high affinity sites. The high affinity sites of HpNikR are equal two by two. It has been proposed that metal binding in the two first sites allows protein “closure” that leads to metal binding in the last two sites. Metal incorporation in the high affinity sites seems to be enough to lead to Protein/DNA complex formation. However metal binding in a second stabilisation site enhances the complex stability. Depending on the operator sequence, the metal and the technique used, holo-HpNikR affinity to DNA varies. With an excess of Ni(II), HpNikR binds pureA and pnixA with a Kd of 2.5 and 1.7 nM but binds weakly pnikR and pexbB. With an excess of Ni(II) and Mn(II), HpNikR binds pnikR and pexbB with a Kd of 38 and 24 nM. Finally, FUR from H.pylori (HpFUR), an iron dependent metalloregulator, has been characterised in order to study its co-regulation with HpNikR on the nikR-exbB intergenic region. HpFUR is a dimer which contains at least two metal binding sites: a structural site and a regulatory site which would allow its activation and its DNA binding.
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Contributor : Caroline Fauquant <>
Submitted on : Friday, February 29, 2008 - 8:55:49 AM
Last modification on : Wednesday, November 4, 2020 - 1:59:40 PM
Long-term archiving on: : Thursday, May 20, 2010 - 7:35:24 PM

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  • HAL Id : tel-00259691, version 1

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Caroline Fauquant. Propriétés de métallation et de liaison à l'ADN de NikR d'Escherichia coli et de NikR et FUR d'Helicobacter pylori. Biochimie [q-bio.BM]. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00259691⟩

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