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Identification of the Escherichia coli K‐12 Nramp orthologue (MntH) as a selective divalent metal ion transporter
Author(s) -
Makui Hortence,
Roig Eva,
Cole Stewart T.,
Helmann John D.,
Gros Philippe,
Cellier Mathieu F. M.
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01774.x
Subject(s) - divalent , escherichia coli , mutant , biology , transporter , biochemistry , biophysics , chemistry , gene , organic chemistry
The Escherichia coli mntH (formerly yfeP ) gene encodes a putative membrane protein (MntH) highly similar to members of the eukaryotic Nramp family of divalent metal ion transporters. To determine the function of E. coli MntH, a null mutant was created and MntH was overexpressed both in wild‐type E. coli and in the metal‐dependent mutant hflB1 (Ts). At the restrictive temperature 42°C, the mntH null mutation reduces the suppression of hflB1 (Ts) thermosensitivity by exogenous divalent metals. Conversely, overexpression of MntH restores growth at 42°C, increases suppression of the ts phenotype by Fe(II) and Ni(II) and renders hflB1 (Ts) cells hypersensitive to Mn(II). Transport studies in intact cells show that MntH selectively facilitates uptake of 54 Mn(II) and 55 Fe(II) in a temperature‐, time‐ and proton‐dependent manner. Competition studies in uptake assays and growth inhibition experiments in hflB1 (Ts) mutants together indicate that MntH is a divalent metal cation transporter of broad substrate specificity. The functional characteristics of MntH suggest that it corresponds to the previously described manganese transporter of E. coli . This study indicates that proton‐dependent divalent metal ion uptake has been preserved in the Nramp family from bacteria to humans.