Molecular Genetics and Genomics

, Volume 274, Issue 3, pp 205–216 | Cite as

Transport of magnesium and other divalent cations: evolution of the 2-TM-GxN proteins in the MIT superfamily

  • Volker Knoop
  • Milena Groth-Malonek
  • Michael Gebert
  • Karolin Eifler
  • Katrin Weyand
Original Paper


In bacteria, magnesium uptake is mainly mediated by the well-characterized CorA type of membrane proteins. In recent years, functional homologues have been characterized in the inner mitochondrial membrane of yeast and mammals (the MRS2/LPE10 type), in the plasma membrane of yeast (the ALR/MNR type) and, as an extended family of proteins, in the model plant Arabidopsis thaliana. Despite generally low sequence similarity, individual proteins can functionally complement each other over large phylogenetic distances. All these proteins are characterized by a universally conserved Gly-Met-Asn (GMN) motif at the end of the first of two conserved transmembrane domains near the C-terminus. Mutations of the GMN motif are known to abolish Mg2+ transport, but the naturally occurring variants GVN and GIN may be associated with the transport of other divalent cations, such as zinc and cadmium, respectively. We refer to this whole class of proteins as the 2-TM-GxN type. The functional membrane channel is thought to be formed by oligomers containing four or five subunits. The wealth of sequence data now available allows us to explore the evolutionary diversification of the basic 2-TM-GxN model within the so-called metal ion transporter (MIT) superfamily. Here we report phylogenetic analyses on more than 360 homologous protein sequences derived from genomic sequences from representatives of all three domains of life. Independent gene duplications have occurred in fungi, plants and proteobacteria at different phylogenetic depths. Moreover, there is ample evidence for several instances of horizontal gene transfer of members of the 2-TM-GxN superfamily in Eubacteria and Archaea. Only single genes of the MRS2 type have been identified in vertebrate genomes. In contrast, 15 members are found in the model plant Arabidopsis thaliana, which appear to have arisen by at least four independent founder events before the diversification of flowering plants. Phylogenetic clade assignment seems to correlate with alterations in the highly conserved sequence around the GMN motif. This presumably forms an integral part of the pore surface, and changes in its structure may result in altered transport capacities for different divalent cations.


Magnesium transport CorA ZntB MRS2 ALR 



Research in the authors’ laboratory on the plant AtMRS2 gene family is supported by the DFG (Deutsche Forschungsgemeinschaft; Grant Kn411/4) in the context of Priority Programme SPP1108 (Plant Membrane Transport).

Supplementary material

438_2005_11_MOESM1_ESM.pdf (173 kb)
Supplementary material


  1. Akman L, Yamashita A, Watanabe H, Oshima K, Shiba T, Hattori M, Aksoy S (2002) Genome sequence of the endocellular obligate symbiont of tsetse flies, Wigglesworthia glossinidia. Nature Genet 32:402–407CrossRefPubMedGoogle Scholar
  2. Altschul SF, Gish W, Miller W, Myers EW, Lipman DJ (1990) Basic local alignment search tool. J Mol Biol 215:403–410CrossRefPubMedGoogle Scholar
  3. Arai M, Mitsuke H, Ikeda M, Xia JX, Kikuchi T, Satake M, Shimizu T (2004) ConPred II: a consensus prediction method for obtaining transmembrane topology models with high reliability. Nucleic Acids Res 32:W390–W393PubMedCrossRefGoogle Scholar
  4. Brayton KA, Kappmeyer LS, Herndon DR, Dark MJ, Tibbals DL, Palmer GH, McGuire TC, Knowles DP Jr (2005) Complete genome sequencing of Anaplasma marginale reveals that the surface is skewed to two superfamilies of outer membrane proteins. Proc Natl Acad Sci USA 102:844–849CrossRefPubMedGoogle Scholar
  5. Bui DM, Gregan J, Jarosch E, Ragnini A, Schweyen RJ (1999) The bacterial magnesium transporter CorA can functionally substitute for its putative homologue Mrs2p in the yeast inner mitochondrial membrane. J Biol Chem 274:20438–20443PubMedCrossRefGoogle Scholar
  6. Busch W, Saier MH (2002) The Transporter Classification (TC) system, 2002. Crit Rev Biochem Mol Biol 37:287–337CrossRefPubMedGoogle Scholar
  7. Caldwell AM, Smith RL (2003) Membrane topology of the ZntB efflux system of Salmonella enterica serovar typhimurium. J Bacteriol 185:374–376PubMedCrossRefGoogle Scholar
  8. Chubanov V, Waldegger S, Schnitzler M, Vitzthum H, Sassen MC, Seyberth HW, Konrad M, Gudermann T (2004) Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia. Proc Natl Acad Sci USA 101:2894–2899CrossRefPubMedGoogle Scholar
  9. Dujon B, et al. (2004) Genome evolution in yeasts. Nature 430:35–44CrossRefPubMedGoogle Scholar
  10. Gardner RC (2003) Genes for magnesium transport. Curr Opin Plant Biol 6:263–267PubMedCrossRefGoogle Scholar
  11. Graschopf A, Stadler JA, Hoellerer MK, Eder S, Sieghardt M, Kohlwein SD, Schweyen RJ (2001) The yeast plasma membrane protein Alr1 controls Mg2+ homeostasis and is subject to Mg2+ -dependent control of its synthesis and degradation. J Biol Chem 276:16216–16222PubMedCrossRefGoogle Scholar
  12. Gregan J, Bui DM, Pillich R, Fink M, Zsurka G, Schweyen RJ (2001a) The mitochondrial inner membrane protein Lpe10p, a homologue of Mrs2p, is essential for magnesium homeostasis and group II intron splicing in yeast. Mol Gen Genet 264:773–781CrossRefPubMedGoogle Scholar
  13. Gregan J, Kolisek M, Schweyen RJ (2001b) Mitochondrial Mg(2+) homeostasis is critical for group II intron splicing in vivo. Genes Dev 15:2229–2237CrossRefPubMedGoogle Scholar
  14. Haynes WJ, Kung C, Saimi Y, Preston RR (2002) An exchanger-like protein underlies the large Mg2+ current in Paramecium. Proc Natl Acad Sci USA 99:15717–15722CrossRefPubMedGoogle Scholar
  15. Hmiel SP, Snavely MD, Miller CG, Maguire ME (1986) Magnesium transport in Salmonella typhimurium: characterization of magnesium influx and cloning of a transport gene. J Bacteriol 168:1444–1450PubMedGoogle Scholar
  16. Hmiel SP, Snavely MD, Florer JB, Maguire ME, Miller CG (1989) Magnesium transport in Salmonella typhimurium: genetic characterization and cloning of three magnesium transport loci. J Bacteriol 171:4742–4751PubMedGoogle Scholar
  17. Kehres DG, Maguire ME (2002) Structure, properties and regulation of magnesium transport proteins. Biometals 15:261–270PubMedCrossRefGoogle Scholar
  18. Kehres DG, Lawyer CH, Maguire ME (1998) The CorA magnesium transporter gene family. Microb Comp Genomics 3:151–169PubMedGoogle Scholar
  19. Kolisek M, Zsurka G, Samaj J, Weghuber J, Schweyen RJ, Schweigel M (2003) Mrs2p is an essential component of the major electrophoretic Mg2+ influx system in mitochondria. EMBO J 22:1235–1244CrossRefPubMedGoogle Scholar
  20. Krogh A, Larsson B, von Heijne G, Sonnhammer EL (2001) Predicting transmembrane protein topology with a hidden Markov model: application to complete genomes. J Mol Biol 305:567–580CrossRefPubMedGoogle Scholar
  21. Kumar S, Tamura K, Nei M (2004) MEGA3: integrated software for molecular evolutionary genetics analysis and sequence alignment. Brief Bioinf 5:150–163CrossRefGoogle Scholar
  22. Li L, Tutone AF, Drummond RS, Gardner RC, Luan S (2001) A novel family of magnesium transport genes in Arabidopsis. Plant Cell 13:2761–2775PubMedCrossRefGoogle Scholar
  23. Liu GJ, Martin DK, Gardner RC, Ryan PR (2002) Large Mg2+ -dependent currents are associated with the increased expression of ALR1 in Saccharomyces cerevisiae. FEMS Microbiol Lett 213:231–237PubMedCrossRefGoogle Scholar
  24. MacDiarmid CW, Gardner RC (1998) Overexpression of the Saccharomyces cerevisiae magnesium transport system confers resistance to aluminum ion. J Biol Chem 273:1727–1732CrossRefPubMedGoogle Scholar
  25. Maguire ME, Cowan JA (2002) Magnesium chemistry and biochemistry. Biometals 15:203–210CrossRefPubMedGoogle Scholar
  26. Mergeay M, Monchy S, Vallaeys T, Auquier V, Benotmane A, Bertin P, Taghavi S, Dunn J, van der Lelie D, Wattiez R (2003) Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes. FEMS Microbiol Rev 27:385–410CrossRefPubMedGoogle Scholar
  27. Moller S, Croning MDR, Apweiler R (2001) Evaluation of methods for the prediction of membrane spanning regions. Bioinformatics 17:646–653CrossRefPubMedGoogle Scholar
  28. Moncrief MB, Maguire ME (1999) Magnesium transport in prokaryotes. J Biol Inorg Chem 4:523–527CrossRefPubMedGoogle Scholar
  29. Nelson KE, et al. (1999) Evidence for lateral gene transfer between Archaea and Bacteria from genome sequence of Thermotoga maritima. Nature 399:323–329CrossRefPubMedGoogle Scholar
  30. Noel-Georis I, Vallaeys T, Chauvaux R, Monchy S, Falmagne R, Mergeay M, Wattiez R (2004) Global analysis of the Ralstonia metallidurans proteome: Prelude for the large-scale study of heavy metal response. Proteomics 4:151–179CrossRefPubMedGoogle Scholar
  31. Obrdlik P, El Bakkoury M, Hamacher T, Cappellaro C, Vilarino C, Fleischer C, Ellerbrok H, Kamuzinzi R, Ledent V, Blaudez D, Sanders D, Revuelta JL, Boles E, Andre B, Frommer WB (2004) K+ channel interactions detected by a genetic system optimized for systematic studies of membrane protein interactions. Proc Natl Acad Sci USA 101:12242–12247CrossRefPubMedGoogle Scholar
  32. Ochman H, Daubin V, Lerat E (2005) A bunch of fun-guys: the whole-genome view of yeast evolution. Trends Genet 21:1–3CrossRefPubMedGoogle Scholar
  33. Rhodes G, Parkhill J, Bird C, Ambrose K, Jones MC, Huys G, Swings J, Pickup RW (2004) Complete nucleotide sequence of the conjugative tetracycline resistance plasmid pFBAOT6, a member of a group of IncU plasmids with global ubiquity. Appl Env Microbiol 70:7497–7510CrossRefGoogle Scholar
  34. Schmitz C, Perraud AL, Johnson CO, Inabe K, Smith MK, Penner R, Kurosaki T, Fleig A, Scharenberg AM (2003) Regulation of vertebrate cellular Mg2+ homeostasis by TRPM7. Cell 114:191–200CrossRefPubMedGoogle Scholar
  35. Schock I, Gregan J, Steinhauser S, Schweyen R, Brennicke A, Knoop V (2000) A member of a novel Arabidopsis thaliana gene family of candidate Mg2+ ion transporters complements a yeast mitochondrial group II intron-splicing mutant. Plant J 24:489–501PubMedCrossRefGoogle Scholar
  36. Schwacke R, Schneider A, van der Graaff E, Fischer K, Catoni E, Desimone M, Frommer WB, Flugge UI, Kunze R (2003) ARAMEMNON, a novel database for Arabidopsis integral membrane proteins. Plant Physiol 131:16–26CrossRefPubMedGoogle Scholar
  37. Shaul O, Hilgemann DW, Almeida-Engler J, Van Montagu M, Inzé D, Galili G (1999) Cloning and characterization of a novel Mg(2+)/H(+) exchanger. EMBO J 18:3973–3980CrossRefPubMedGoogle Scholar
  38. Smith RL, Maguire ME (1998) Microbial magnesium transport: unusual transporters searching for identity. Mol Microbiol 28:217–226CrossRefPubMedGoogle Scholar
  39. Smith RL, Banks JL, Snavely MD, Maguire ME (1993) Sequence and topology of the CorA magnesium transport systems of Salmonella typhimurium and Escherichia coli. Identification of a new class of transport protein. J Biol Chem 268:14071–14080PubMedGoogle Scholar
  40. Smith RL, Thompson LJ, Maguire ME (1995) Cloning and characterization of MgtE, a putative new class of Mg2+ transporter from Bacillus firmus OF4. J Bacteriol 177:1233–1238PubMedGoogle Scholar
  41. Smith RL, Gottlieb E, Kucharski LM, Maguire ME (1998a) Functional similarity between archaeal and bacterial CorA magnesium transporters. J Bacteriol 180:2788–2791Google Scholar
  42. Smith RL, Szegedy MA, Kucharski LM, Walker C, Wiet RM, Redpath A, Kaczmarek MT, Maguire ME (1998b) The CorA Mg2+ transport protein of Salmonella typhimurium—mutagenesis of conserved residues in the third membrane domain identifies a Mg2+ pore. J Biol Chem 273:28663–28669PubMedCrossRefGoogle Scholar
  43. Snavely MD, Florer JB, Miller CG, Maguire ME (1989) Magnesium transport in Salmonella typhimurium: 28 Mg2+ transport by the CorA, MgtA, and MgtB systems. J Bacteriol 171:4761–4766PubMedGoogle Scholar
  44. Sonnhammer EL, von Heijne G, Krogh A (1998) A hidden Markov model for predicting transmembrane helices in protein sequences. Proc Int Conf Intell Syst Mol Biol 6:175–182PubMedGoogle Scholar
  45. Szegedy MA, Maguire ME (1999) The CorA Mg2+ transport protein of Salmonella typhimurium—mutagenesis of conserved residues in the second membrane domain. J Biol Chem 274:36973–36979CrossRefPubMedGoogle Scholar
  46. Townsend DE, Esenwine AJ, George J, III, Bross D, Maguire ME, Smith RL (1995) Cloning of the mgtE Mg2+ transporter from Providencia stuartii and the distribution of mgtE in gram-negative and gram-positive bacteria. J Bacteriol 177:5350–5354PubMedGoogle Scholar
  47. Warren MA, Kucharski LM, Veenstra A, Shi L, Grulich PF, Maguire ME (2004) The CorA Mg2+ transporter is a homotetramer. J Bacteriol 186:4605–4612PubMedCrossRefGoogle Scholar
  48. Wiesenberger G, Waldherr M, Schweyen RJ (1992) The nuclear gene MRS2 is essential for the excision of group II introns from yeast mitochondrial transcripts in vivo. J Biol Chem 267:6963–6969PubMedGoogle Scholar
  49. Worlock AJ, Smith RL (2002) ZntB is a novel Zn2+ transporter in Salmonella enterica serovar Typhimurium. J Bacteriol 184:4369–4373CrossRefPubMedGoogle Scholar
  50. Zsurka G, Gregan J, Schweyen RJ (2001) The human mitochondrial Mrs2 protein functionally substitutes for its yeast homologue, a candidate magnesium transporter. Genomics 72:158–168PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Volker Knoop
    • 1
  • Milena Groth-Malonek
    • 1
  • Michael Gebert
    • 1
  • Karolin Eifler
    • 1
  • Katrin Weyand
    • 1
  1. 1.Abteilung Molekulare Evolution, Institut für Zelluläre und Molekulare Botanik (IZMB)Universität BonnBonnGermany

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