Metal ion determinants of conantokin dimerization as revealed in the X-ray crystallographic structure of the Cd2+/Mg2+–con-T[K7γ] complex

  • Sara E. Cnudde
  • Mary Prorok
  • Francis J. Castellino
  • James H. Geiger
Original Paper

Abstract

Predatory sea snails from the Conus family produce a variety of venomous small helical peptides called conantokins that are rich in γ-carboxyglutamic acid (Gla) residues. As potent and selective antagonists of the N-methyl-d-aspartate receptor, these peptides are potential therapeutic agents for a variety of neurological conditions. The two most studied members of this family of peptides are con-G and con-T. Con-G has Gla residues at sequence positions 3, 4, 7, 10, and 14, and requires divalent cation binding to adopt a helical conformation. Although both Ca2+ and Mg2+ can fulfill this role, Ca2+ induces dimerization of con-G, whereas the Mg2+-complexed peptide remains monomeric. A variant of con-T, con-T[K7γ] (γ is Gla), contains Gla residues at the same five positions as in con-G and behaves very similarly with respect to metal ion binding and dimerization; each peptide binds two Ca2+ ions and two Mg2+ ions per helix. To understand the difference in metal ion selectivity, affinity, and the dependence on Ca2+ for dimer formation, we report here the structure of the monomeric Cd2+/Mg2+–con-T[K7γ] complex, and, by comparison with the previously published con-T[K7γ]/Ca2+ dimer structure, we suggest explanations for both metal ion binding site specificity and metal-ion-dependent dimerization.

Keywords

Crystallography Conantokins γ-Carboxyglutamic acid Peptide α-helix 

Abbreviations

Con-G

Conantokin-G

Con-T

Conantokin-T

Gla

γ-Carboxyglutamate

NMDAR

N-Methyl-d-aspartate receptor

Notes

Acknowledgments

We thank the following for financial support: GR-179 (085P100549) from the Michigan Economic Development Corporation (to J.H.G.), NIH Grant HL019982 (to F.J.C.), and NIH Grant GM0638947 (to J.H.G.). CCDC-667723 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.

References

  1. 1.
    McIntosh J, Olivera BM, Cruz L, Gray W (1984) J Biol Chem 259:14343–14346PubMedGoogle Scholar
  2. 2.
    Haack JA, Rivier J, Parks TN, Mena EE, Cruz LJ, Olivera BM (1990) J Biol Chem 265:6025–6029PubMedGoogle Scholar
  3. 3.
    Prorok M, Warder SE, Blandl T, Castellino FJ (1996) Biochemistry 35:16528–16534CrossRefPubMedGoogle Scholar
  4. 4.
    Skjaerbaek N, Nielsen KJ, Lewis RJ, Alewood P, Craik DJ (1997) J Biol Chem 272:2291–2299CrossRefPubMedGoogle Scholar
  5. 5.
    Dai Q, Prorok M, Castellino FJ (2004) J Mol Biol 336:731–744CrossRefPubMedGoogle Scholar
  6. 6.
    Dai Q, Castellino FJ, Prorok M (2004) Biochemistry 43:13225–13232CrossRefPubMedGoogle Scholar
  7. 7.
    Cnudde SE, Prorok M, Dai Q, Castellino FJ, Geiger JH (2007) J Am Chem Soc 129:1586–1593CrossRefPubMedGoogle Scholar
  8. 8.
    Prorok M, Castellino FJ (1998) J Biol Chem 273:19573–19578CrossRefPubMedGoogle Scholar
  9. 9.
    Dai QY, Sheng ZY, Geiger JH, Castellino FJ, Prorok M (2007) J Biol Chem 282:12641–12649CrossRefPubMedGoogle Scholar
  10. 10.
    Cerasoli E, Sharpe BK, Woolfson DN (2005) J Am Chem Soc 127:15008–15009. doi: 10.1021/ja0543604 CrossRefPubMedGoogle Scholar
  11. 11.
    Gribbon C, Channon KJ, Zhang WJ, Banwell EF, Bromley EHC, Chaudhuri JB, Oreffo ROC, Woolfson DN (2008) Biochemistry 47:10365–10371. doi: 10.1021/bi801072s CrossRefPubMedGoogle Scholar
  12. 12.
    Shekhawat SS, Porter JR, Sriprasad A, Ghosh I (2009) J Am Chem Soc 131:15284–15290. doi: 10.1021/ja9050857 CrossRefPubMedGoogle Scholar
  13. 13.
    Zimenkov Y, Dublin SN, Ni R, Tu RS, Breedveld V, Apkarian RP, Conticello VP (2006) J Am Chem Soc 128:6770–6771. doi: 10.1021/ja0605974 CrossRefPubMedGoogle Scholar
  14. 14.
    Otwinowski ZaM W (1997) Methods Enzymol 276:307–326CrossRefGoogle Scholar
  15. 15.
    McCoy AJ, Grosse-Kunstleve RW, Storoni LC, Read RJ (2005) Acta Crystallogr D 61:458–464CrossRefPubMedGoogle Scholar
  16. 16.
    Collaborative Computational Project N (1994) Acta Crystallogr D 50:760–763CrossRefGoogle Scholar
  17. 17.
    Matthews BW (1968) J Mol Biol 33:491–497CrossRefPubMedGoogle Scholar
  18. 18.
    Sheldrick GM, Schneider TR (1997) In: Sweet RM, Carter CW Jr (eds) Methods in enzymology. Academic Press, Orlando, pp 319–343Google Scholar
  19. 19.
    Gowd KH, Twede V, Watkins M, Krishnan KS, Teichert RW, Bulaj G, Olivera BM (2008) Toxicon 52:203–213. doi: 10.1016/j.toxicon.2008.04.178 CrossRefPubMedGoogle Scholar
  20. 20.
    Teichert RW, Jimenez EC, Twede V, Watkins M, Hollmann M, Bulaj G, Olivera BM (2007) J Biol Chem 282:36905–36913CrossRefPubMedGoogle Scholar
  21. 21.
    Twede VD, Teichert RW, Walker CS, Gruszczynski P, Kazmierkiewicz R, Bulaj G, Olivera BM (2009) Biochemistry 48:4063–4073. doi: 10.1021/bi802259a CrossRefPubMedGoogle Scholar
  22. 22.
    Prorok M, Castellino FJ (2001) Curr Drug Targ 2:313–322CrossRefGoogle Scholar

Copyright information

© SBIC 2010

Authors and Affiliations

  • Sara E. Cnudde
    • 1
  • Mary Prorok
    • 2
  • Francis J. Castellino
    • 2
  • James H. Geiger
    • 1
  1. 1.Department of ChemistryMichigan State UniversityEast LansingUSA
  2. 2.Department of Chemistry and Biochemistry, W.M. Keck Center for Transgene ResearchUniversity of Notre DameNotre DameUSA

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