Iron transport by Nramp2/DMT1: pH regulation of transport by 2 histidines in transmembrane domain 6

Lam-Yuk-Tseung, Steven; Govoni, Gregory; Forbes, John; Gros, Philippe

doi:10.1182/blood-2002-07-2108

Cited by 101 publications

(112 citation statements)

References 49 publications

(72 reference statements)

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“…1C). Loss of a metal-coordinating residue that uses oxygen to bind the metal, D56 or N59, was detrimental to Co 2+ uptake, consistent with the previously demonstrated importance of these residues to the transport of Co 2+ , Fe 2+ , Mn 2+ , and Cd 2+ in bacterial and eukaryotic Nramp homologs (9,(17)(18)(19)(20).…”

Section: Significancesupporting

confidence: 67%

Conserved methionine dictates substrate preference in Nramp-family divalent metal transporters

Bozzi

Bane

Weihofen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

110

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Natural resistance-associated macrophage protein (Nramp) family transporters catalyze uptake of essential divalent transition metals like iron and manganese. To discriminate against abundant competitors, the Nramp metal-binding site should favor softer transition metals, which interact either covalently or ionically with coordinating molecules, over hard calcium and magnesium, which interact mainly ionically. The metal-binding site contains an unusual, but conserved, methionine, and its sulfur coordinates transition metal substrates, suggesting a vital role in their transport. Using a bacterial Nramp model system, we show that, surprisingly, this conserved methionine is dispensable for transport of the physiological manganese substrate and similar divalents iron and cobalt, with several small amino acid replacements still enabling robust uptake. Moreover, the methionine sulfur's presence makes the toxic metal cadmium a preferred substrate. However, a methionine-to-alanine substitution enables transport of calcium and magnesium. Thus, the putative evolutionary pressure to maintain the Nramp metal-binding methionine likely exists because it-more effectively than any other amino acid-increases selectivity for low-abundance transition metal transport in the presence of high-abundance divalents like calcium and magnesium.transition metals | MntH | divalent metal transporter DMT1 | hard-soft acid-base theory | ion selectivity filters A ll organisms require transition metal ions as cofactors in proteins that perform a variety of essential cellular tasks. Through evolution, organisms have developed mechanisms to acquire, transport, and safely store essential metals such as manganese, iron, cobalt, and zinc. The natural resistance-associated macrophage protein (Nramp) family of metal transporters represents a common transition metal acquisition strategy conserved across all kingdoms of life (1). The first discovered mammalian Nramp (Nramp1) is expressed in phagosomal membranes and likely extracts essential metals to help kill engulfed pathogens (2, 3). Mammals use Nramp2, an essential gene also called DMT1, to absorb dietary iron into the enterocytes that line the small intestine (4) and to extract iron from transferrin-containing endosomes in all tissues. Bacteria express their own Nramp homologs, which they typically use to scavenge manganese and other first row divalent transition metals (5, 6). Last, most plants have several Nramp homologs that take up iron and manganese, the essential cofactor in photosystem II, from the soil or vacuolar stores (7,8).Nramps are generally thought to function as metal-proton symporters (1) and are able to bind and/or transport a wide range of divalent transition metal substrates, including the biologically useful metals Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ , as well as the toxic heavy metals Cd 2+ , Pb 2+ , and Hg 2+ (4, 9-13). Nramps do discriminate against the divalent alkaline earth metal ions Mg 2+ and Ca 2+ (9, 14), which are typically several orders of magnitude mor...

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Section: Significancesupporting

confidence: 67%

Conserved methionine dictates substrate preference in Nramp-family divalent metal transporters

Bozzi

Bane

Weihofen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

110

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“…Slc11a2-nonIRE protein expression complemented the EGTA-induced growth deficiency (Fig. 1E, dotted triangle) as previously reported (19,20,38). The growth deficiency of smf1⌬/smf2⌬/smf3⌬ was also complemented by expression of the Slc11a2-IRE protein, which has not previously been expressed in yeast (Fig.…”

Section: Slc11a2 But Not Slc11a1supporting

confidence: 64%

Evolution of Differences in Transport Function in Slc11a Family Members

Techau

Taubas

Popoff

et al. 2007

Journal of Biological Chemistry

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Slc11a1 (formerly Nramp1) is a proton/divalent cation transporter that regulates cation homeostasis in macrophages. Slc11a2 mediates divalent cation uptake via the gut and delivery into cells. The mode of action of the two transporters remains controversial. Heterologous expression in frog oocytes shows Slc11a2 is a symporter, whereas Slc11a1 is an antiporter fluxing divalent cations against the proton gradient. This explains why Slc11a2, but not Slc11a1, can complement EGTA sensitivity in smf1⌬/smf2⌬/smf3⌬ yeast. However, some studies of transport in mammalian cells suggest Slc11a1 is a symporter. We now demonstrate that Slc11a1, but not Slc11a2, complements a divalent cation stress phenotype in bsd2⌬/rer1⌬ yeast. This is the first description of a yeast complementation assay for Slc11a1 function. Given the prior demonstration in frog oocytes that Slc11a1 acts as an antiporter, the most plausible interpretation of the data is that Slc11a1 is rescuing bsd2⌬/rer1⌬ yeast by exporting divalent cations. Chimaeras define the N terminus, and a segment of the protein core preceding transmembrane domain 9 through transmembrane domain 12, as important in rescuing the divalent cation stress phenotype. EGTA sensitivity and divalent cation stress phenotypes in yeast expressing Slc11a orthologues show that symport activity is ancestral. Molecular changes that mediate rescue of the divalent cation stress phenotype post-date frogs and co-evolved with Slc11a1 orthologues that regulate divalent cation homeostasis in macrophages and resistance to infection in chickens and mammals.Slc11a1 (formerly Ity/Lsh/Bcg/Nramp1) is a proton/divalent cation transporter with 12 putative transmembrane domains (TMD) 4 (1) that localizes to late endosomes and lysosomes of macrophages (2, 3) and dendritic cells (4), and tertiary granules of neutrophils (5). It is recruited to phagosome membranes in macrophages infected with Mycobacterium (2, 3) or Leishmania (3), and regulates cellular divalent cation homeostasis (6, 7). Polymorphisms at murine Slc11a1 and human SLC11A1 contribute to susceptibility to numerous infectious and autoimmune diseases (8, 9). Slc11a2 (also Nramp2/DMT1/DCT1) shares 64% amino acid identity with Slc11a1 (10) and regulates divalent cation uptake via the gut and delivery of iron into multiple cell types (11,12). Different isoforms can be distinguished by different C-terminal amino acid sequences, and by the presence or absence of an iron response element located in the 3Ј-untranslated region of the mRNA (13). The IRE-containing isoform (Slc11a2-IRE) is expressed predominantly in epithelial cells and localizes to late endosome/lysosomes, whereas the non-IRE-containing isoform (Slc11a2-nonIRE) is expressed in blood cell lineages and localizes to early endosomes (13). Both isoforms localize to their respective endosomal compartments and to apical membranes when expressed in polarized MadinDarby canine kidney cells (13). Mutation at Slc11a2 in mice and rats is associated with microcytic anemia (14, 15).Fe 2ϩ , Zn 2ϩ , Mn 2ϩ , Co ...

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“…A previously described full-length cDNA clone for Nramp2 was also used. 39 Statistical analysis All studies were repeated two or more times with three to five animals per group. Statistical significance between groups was tested by a two-sample Student's t-test.…”

Section: Northern Blot Analysismentioning

confidence: 99%

Phenotypic expression of pyruvate kinase deficiency and protection against malaria in a mouse model

Min‐Oo

Fortin

et al. 2004

Genes Immun

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The recombinant congenic mouse strains AcB55 and AcB61 are extremely resistant to malaria (Plasmodium chabaudi AS) despite the presence of susceptibility alleles at the known Char1/Char2 resistance loci. Resistance in AcB55 and AcB61 is controlled by a locus on chromosome 3 (Char4) shown to be allelic with or tightly linked to a loss-of-function mutation in pyruvate kinase (Pklr). AcB55 and AcB61 show important splenomegaly prior to infection caused by the expansion of the red pulp, and display histological signs of extramedullary erythropoiesis in the liver. Examination of splenic cell populations by flow cytometry demonstrates elevated numbers of TER119-positive erythroid precursor cells (430% of total spleen cells), while RNA expression studies show elevated expression of erythrocyte-specific transcripts such as globin, transferrin receptor, and Nramp2/Slc11a2 in the spleen of both strains. Hematological profiling in both strains is consistent with the presence of anemia as evidenced by low total erythrocyte counts, decreased hemoglobin, as well as abnormally high numbers of circulating reticulocytes (15-20%). These results strongly suggest that the mutant Pklr allele (Pklr 269A ) of AcB55/61 strains causes hemolytic anemia compensated by constitutive erythropoiesis, which in turn protects the mice against P. chabaudi infection. The possible molecular basis of the Pklr protective effect is discussed and is under current investigation in these two strains.

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Iron transport by Nramp2/DMT1: pH regulation of transport by 2 histidines in transmembrane domain 6

Cited by 101 publications

References 49 publications

Conserved methionine dictates substrate preference in Nramp-family divalent metal transporters

Conserved methionine dictates substrate preference in Nramp-family divalent metal transporters

Evolution of Differences in Transport Function in Slc11a Family Members

Phenotypic expression of pyruvate kinase deficiency and protection against malaria in a mouse model

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