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Issue 4, 2015
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Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake

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Abstract

Bacteria require nickel transporters for the synthesis of Ni-containing metalloenzymes in natural, low nickel habitats. In this work we carry out functional and topological characterization of Rhizobium leguminosarum HupE, a nickel permease required for the provision of this element for [NiFe] hydrogenase synthesis. Expression studies in the Escherichia coli nikABCDE mutant strain HYD723 revealed that HupE is a medium-affinity permease (apparent Km 227 ± 21 nM; Vmax 49 ± 21 pmol Ni2+ min−1 mg−1 bacterial dry weight) that functions as an energy-independent diffusion facilitator for the uptake of Ni(II) ions. This Ni2+ transport is not inhibited by similar cations such as Mn2+, Zn2+, or Co2+, but is blocked by Cu2+. Analysis of site-directed HupE mutants allowed the identification of several residues (H36, D42, H43, F69, E90, H130, and E133) that are essential for HupE-mediated Ni uptake in E. coli cells. By using translational fusions to reporter genes we demonstrated the presence of five transmembrane domains with a periplasmic N-terminal domain and a C-terminal domain buried in the lipid bilayer. The periplasmic N-terminal domain contributes to stability and functionality of the protein.

Graphical abstract: Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake

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Publication details

The article was received on 15 Nov 2014, accepted on 27 Jan 2015 and first published on 28 Jan 2015


Article type: Paper
DOI: 10.1039/C4MT00298A
Citation: Metallomics, 2015,7, 691-701
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    Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake

    M. Albareda, A. Rodrigue, B. Brito, T. Ruiz-Argüeso, J. Imperial, M. Mandrand-Berthelot and J. Palacios, Metallomics, 2015, 7, 691
    DOI: 10.1039/C4MT00298A

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