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Crystal structure of the CorA Mg2+ transporter


The magnesium ion, Mg2+, is essential for myriad biochemical processes and remains the only major biological ion whose transport mechanisms remain unknown. The CorA family of magnesium transporters is the primary Mg2+ uptake system of most prokaryotes1,2,3 and a functional homologue of the eukaryotic mitochondrial magnesium transporter4. Here we determine crystal structures of the full-length Thermotoga maritima CorA in an apparent closed state and its isolated cytoplasmic domain at 3.9 Å and 1.85 Å resolution, respectively. The transporter is a funnel-shaped homopentamer with two transmembrane helices per monomer. The channel is formed by an inner group of five helices and putatively gated by bulky hydrophobic residues. The large cytoplasmic domain forms a funnel whose wide mouth points into the cell and whose walls are formed by five long helices that are extensions of the transmembrane helices. The cytoplasmic neck of the pore is surrounded, on the outside of the funnel, by a ring of highly conserved positively charged residues. Two negatively charged helices in the cytoplasmic domain extend back towards the membrane on the outside of the funnel and abut the ring of positive charge. An apparent Mg2+ ion was bound between monomers at a conserved site in the cytoplasmic domain, suggesting a mechanism to link gating of the pore to the intracellular concentration of Mg2+.

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Figure 1: Structure of the CorA Mg 2+ channel.
Figure 2: Analysis of the CorA pore.
Figure 3: Electrostatic view of CorA.
Figure 4: Pore dimensions.
Figure 5: Electron density corresponding to protein and bound magnesium.


  1. 1

    Nelson, D. L. & Kennedy, E. P. Magnesium transport in Escherichia coli. Inhibition by cobaltous ion. J. Biol. Chem. 246, 3042–3049 (1971)

    CAS  PubMed  Google Scholar 

  2. 2

    Hmiel, S. P., Snavely, M. D., Miller, C. G. & Maguire, M. E. Magnesium transport in Salmonella typhimurium: Characterization of magnesium influx and cloning of a transport gene. J. Bacteriol. 168, 1444–1450 (1986)

    CAS  Article  Google Scholar 

  3. 3

    Bui, D. M., Gregan, J., Jarosch, E., Ragnini, A. & Schweyen, R. J. The bacterial magnesium transporter CorA can functionally substitute for its putative homologue Mrs2p in the yeast inner mitochondrial membrane. J. Biol. Chem. 274, 20438–20443 (1999)

    CAS  Article  Google Scholar 

  4. 4

    Kehres, D. G. & Maguire, M. E. Structure, properties and regulation of magnesium transport proteins. Biometals 15, 261–270 (2002)

    CAS  Article  Google Scholar 

  5. 5

    Kehres, D. G., Lawyer, C. H. & Maguire, M. E. The CorA magnesium transporter gene family. Microb. Compar. Genom. 43, 151–169 (1998)

    Article  Google Scholar 

  6. 6

    Worlock, A. J. & Smith, R. L. ZntB is a novel Zn2+ transporter in Salmonella enterica serovar Typhimurium. J. Bacteriol. 184, 4369–4373 (2002)

    CAS  Article  Google Scholar 

  7. 7

    Gardner, R. C. Genes for magnesium transport. Curr. Opin. Plant Biol. 6, 263–267 (2003)

    CAS  Article  Google Scholar 

  8. 8

    Cordes, F. S., Bright, J. N. & Sansom, M. S. Proline-induced distortions of transmembrane helices. J. Mol. Biol. 323, 951–960 (2002)

    CAS  Article  Google Scholar 

  9. 9

    Tieleman, D. P., Shrivastava, I. H., Ulmschneider, M. R. & Sansom, M. S. Proline-induced hinges in transmembrane helices: possible roles in ion channel gating. Proteins 44, 63–72 (2001)

    CAS  Article  Google Scholar 

  10. 10

    Knoop, V., Groth-Malonek, M., Gebert, M., Eifler, K. & Weyand, K. Transport of magnesium and other divalent cations: evolution of the 2-TM-GxN proteins in the MIT superfamily. Mol. Genet. Genom. 274, 205–216 (2005)

    CAS  Article  Google Scholar 

  11. 11

    Doyle, D. A. Molecular insights into ion channel function. Mol. Membr. Biol. 21, 221–225 (2004)

    CAS  Article  Google Scholar 

  12. 12

    Roux, B. & MacKinnon, R. The cavity and pore helices in the KcsA K+ channel: electrostatic stabilization of monovalent cations. Science 285, 100–102 (1999)

    CAS  Article  Google Scholar 

  13. 13

    Doyle, D. A. et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280, 69–77 (1998)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Kuo, A. et al. Crystal structure of the potassium channel KirBac1.1 in the closed state. Science 300, 1922–1926 (2003)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Chang, G., Spencer, R. H., Lee, A. T., Barclay, M. T. & Rees, D. C. Structure of the MscL homolog from Mycobacterium tuberculosis: A gated mechanosensitive ion channel. Science 282, 2220–2226 (1998)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Miyazawa, A., Fujiyoshi, Y. & Unwin, N. Structure and gating mechanism of the acetylcholine receptor pore. Nature 423, 949–955 (2003)

    ADS  CAS  Article  Google Scholar 

  17. 17

    MacKinnon, R. Potassium channels and the atomic basis for selective ion conduction. Biosci. Rep. 24, 75–100 (2004)

    CAS  Article  Google Scholar 

  18. 18

    Maguire, M. E. & Cowan, J. A. Mg2+ chemistry and biochemistry. Biometals 15, 203–210 (2002)

    CAS  Article  Google Scholar 

  19. 19

    Snavely, M. D., Florer, J. B., Miller, C. G. & Maguire, M. E. Magnesium transport in Salmonella typhimurium: 28Mg2+ transport by the CorA, MgtA, and MgtB systems. J. Bacteriol. 171, 4761–4766 (1989)

    CAS  Article  Google Scholar 

  20. 20

    Kucharski, L. M., Lubbe, W. J. & Maguire, M. E. Cation hexaammines are selective and potent inhibitors of the CorA magnesium transport system. J. Biol. Chem. 275, 16767–16773 (2000)

    CAS  Article  Google Scholar 

  21. 21

    Szegedy, M. A. & Maguire, M. E. The CorA Mg2+ transport protein of Salmonella typhimurium. Mutagenesis of conserved residues in the second membrane domain. J. Biol. Chem. 274, 36973–36979 (1999)

    CAS  Article  Google Scholar 

  22. 22

    Langosch, D., Thomas, L. & Betz, H. Conserved quaternary structure of ligand-gated ion channels: the postsynaptic glycine receptor is a pentamer. Proc. Natl Acad. Sci. USA 85, 7394–7398 (1988)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Lester, H. A. The permeation pathway of neurotransmitter-gated ion channels. Annu. Rev. Biophys. Biomol. Struct. 21, 267–292 (1992)

    CAS  Article  Google Scholar 

  24. 24

    Delano, W. L. PyMOL (cited 19 October 2005).

  25. 25

    Korolev, S. et al. The crystal structure of spermidine synthase with a multisubstrate adduct inhibitor. Nature Struct. Biol. 9, 27–31 (2002)

    CAS  Article  Google Scholar 

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The research was supported by grants from Genome Canada, the National Institutes of Health, the US Department of Energy, Office of Biological and Environmental Research, and the Structural Genomics Consortium. We thank M. McMillan and Y. Kim for assistance in collecting data, and A. Savchenko and the Indians and Red Wings screening teams for their guidance. We also thank C. Charky and D. Bouchard at Nextal Biotechnologies for their assistance throughout our membrane protein crystallization efforts.

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Corresponding authors

Correspondence to Michael E. Maguire or Aled M. Edwards.

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Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Figure 1

Ribbon diagram of the CorA soluble domain. (JPG 62 kb)

Supplementary Figure 2

Close-up view of the CorA periplasmic surface. (JPG 53 kb)

Supplementary Figure 3

Secondary structure predictions of CorA homologues. (JPG 137 kb)

Supplementary Figure 4

There are over 250 CorA homologs and around 200 Mrs2 homologs listed in the current NCBI and Swiss-Prot databases. (JPG 307 kb)

Supplementary Figure 5

View of the electrostatic potential of the CorA surface. (JPG 59 kb)

Supplementary Figure Legends

This file contains legends to the Supplementary Figures. (DOC 30 kb)

Supplementary Data

This file contains Supplementary Methods, Table 1 and additional references. (DOC 60 kb)

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Lunin, V., Dobrovetsky, E., Khutoreskaya, G. et al. Crystal structure of the CorA Mg2+ transporter. Nature 440, 833–837 (2006).

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