Identification of the Escherichia coli K‐12 Nramp orthologue (MntH) as a selective divalent metal ion transporter

Abstract

SummaryThe 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 428C, the mntH null mutation reduces the suppression of hflB1(Ts) thermosensitivity by exogenous divalent metals. Conversely, overexpression of MntH restores growth at 428C, 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.

Identification of genetic loci controlling bacterial clearance in experimental Salmonella enteritidis infection: an unexpected role of Nramp1 (Slc11a1) in the persistence of infection in mice

“…Ses2 explained 6% of the genetic variance and Ses3, 4% (Table 2). In these cases also, the C57BL/6J allele is protective and contributes in a recess- 33,9,36,25 D7Mit76,83,62,31,323,38,237,44,189 D8Mit3,41,56 D9Mit218,25,306,37 D10Mit80,38,42,10,205 D11Mit77,20,5,4,124,61 D12Mit182,49,12,59,46,60,14,Nds2 D13Mit236,139,147,30,36,151 D14Mit11,52,30 D15Mit12,26,46,47,29,42,242,159,35 D16Mit81,4,47,…”

“…9,14,17 Nramp1 is part of an ancient family of proteins with highly conserved members in mammals, birds, invertebrates, plants, fungi and even bacteria. [18][19][20][21][22][23][24][25][26] Nramp1 is an integral membrane phosphoglycoprotein located in the late endosome/lysosome compartment of resting macrophages and is recruited to the phagosomal membrane during phagosome maturation 27 that encodes for a divalent-cation transporter. 28 Several additional loci have been found to exert some control during the late phase of infection through their effects on the acquired immune responses.…”

Control of bacterial iron homeostasis by manganese

“…Numerous members of the Nramp family of eukaryotic and prokaryotic proteins transport both Mn 2+ and Fe 2+ into cells (2)(3)(4)(5). Growth of an Escherichia coli iron-transport mutant is inhibited in an mntH background, suggesting that manganese may substitute for iron in cells (6).…”

Overexpression, purification, and site-directed spin labeling of the Nramp metal transporter from Mycobacterium leprae

“…Thus, our finding that divalent metals increase levels of protein in the membrane by 90-120% is significant. Recent studies on prokaryotic Nramp homologues from S. typhimurium and E. coli have shown that transcription of these proteins is diminished when the cells are exposed to divalent transition ions (11,12), presumably caused by promoter elements that recognize divalent metals (12). In our case, we suspect that the metals serve a substrate-protective role, through structural stabilization, which may benefit insertion and͞or shield the protein from proteases.…”

“…Recently, the manganese transport functions of bacterial Nramp homologues (MntH) from Escherichia coli, Salmonella typhimurium, and M. tuberculosis have been demonstrated (11)(12)(13). Thus the resistance of the host against the pathogen, and the pathogenicity of the microorganism, may depend on the performance of the individual Nramp or homologous protein.…”