Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake. Issue 4 (5th February 2015)

• Record Type: Journal Article
• Authors: Albareda, Marta; Rodrigue, Agnès; Brito, Belén; Ruiz-Argüeso, Tomás; Imperial, Juan; Mandrand-Berthelot, Marie-Andrée; Palacios, Jose
• Is Part Of: Metallomics. Volume 7:Issue 4(2015:Apr.)
• Page Start: 691
• Page End: 701
• Publication Date: 2015-02-05
• Subjects: Metals -- Physiological effect -- Periodicals; 572.51
• DOI: 10.1039/c4mt00298a
• Languages: English
• ISSNs: 1756-5901

Abstract

Abstract : Functional and topological analysis of Rhizobium leguminosarum HupE, the founding member of the HupE/UreJ family of nickel permeases, provides new hints on how bacteria manage nickel provision for metalloenzyme synthesis. 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 K m 227 ± 21 nM; V max 49 ± 21 pmol Ni 2+ min −1 mg −1 bacterial dry weight) that functions as an energy-independent diffusion facilitator for the uptake of Ni(ii ) ions. This Ni 2+ transport is not inhibited by similar cations such as Mn 2+, Zn 2+, or Co 2+, but is blocked by Cu 2+ . 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.