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

Marta Albareda (1) , Agnès Rodrigue (2, 3) , Belén Brito (1) , Tomás Ruiz-Argüeso (1) , Juan Imperial (1) , Marie-Andrée Mandrand-Berthelot (2, 3) , Jose Palacios (1)

1 UPM - Universidad Politécnica de Madrid
2 MAP - Microbiologie, adaptation et pathogénie
3 MTSB - Trafic et signalisation membranaires chez les bactéries

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 AE 21 nM; V max 49 AE 21 pmol Ni 2+ min À1 mg À1 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.

Domaines: Biologie moléculaire; Biochimie [q-bio.BM]; Génomique, Transcriptomique et Protéomique [q-bio.GN]; Bactériologie

Marta Albareda, Agnès Rodrigue, Belén Brito, Tomás Ruiz-Argüeso, Juan Imperial, et al.. Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake. Metallomics, 2015, 7 (4), pp.691 - 701. ⟨10.1039/c4mt00298a⟩. ⟨hal-01652730⟩