The Journal of Membrane Biology

, Volume 48, Issue 4, pp 357–364 | Cite as

Binding of radioactively labeled saxitoxin to the squid giant axon

  • G. R. Strichartz
  • R. B. Rogart
  • J. M. Ritchie
Article

Summary

The binding of saxitoxin, a specific inhibitor of the sodium conductance in excitable membranes, has been measured in giant axons from the squid,Loligo pealei. Binding was studied by labeling saxitoxin with tritium, using a solvent-exchange technique, and measuring the toxin uptake by liquid scintillation counting. Total toxin binding is the sum of a saturable, hyperbolic binding component, with a dissociation constant at 2–4°C of 4.3±1.7nm (meanse), and a linear, nonsaturable component. The density of saturable binding sites is 166±20.4 μm−2. From this density and published values of the maximum sodium conductance, the conductance per toxin site is estimated to be about 7 pS, assuming sequential activation and inactivation processes (F. Bezanilla & C.M. Armstrong, 1977,J. Gen. Physiol.70: 549). This single site conductance value of 7 pS is in close agreement with estimates of the conductance of one open sodium channel from measurements of gating currents and of noise on squid giant axons, and is consistent with the hypothesis that one saxitoxin molecule binds to one sodium channel.

Keywords

Tritium Sodium Channel Giant Axon Saxitoxin Binding Component 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Almers, W., Levinson, S.R. 1975. Tetrodotoxin binding to normal and depolarized frog mucsle and the conductance of a single sodium channel.J. Physiol. (London) 247:483Google Scholar
  2. Armstrong, C.M. 1975. Ionic pores, gates and gating currents.Q. Rev. Biophys. 7:179Google Scholar
  3. Bezanilla, F., Armstrong, C.M. 1977. Inactivation of the sodium channel I. sodium current experiments.J. Gen. Physiol. 70:549Google Scholar
  4. Colquhoun, D., Henderson, R., Ritchie, J.M. 1972. The binding of labelled tetrodotoxin to non-myelinated nerve fibres.J. Physiol. (London) 227:95Google Scholar
  5. Colquhoun, D., Ritchie, J.M. 1972. The interaction at equilibrium between tetrodotoxin and mammalian non-myelinated nerve fibres.J. Physiol. (London) 221:533Google Scholar
  6. Conti, F., Felice, L.J. de, Wanke, E. 1975. Potassium and sodium, current noise in the membrane of the squid giant axon.J. Physiol. (London) 248:45Google Scholar
  7. Cuervo, L.A., Adelman, W.J. 1970. Equilibrium and kinetic properties of the interaction between tetrodotoxin and excitable membrane of the squid giant axon.J. Gen. Physiol. 55:309Google Scholar
  8. Evans, M.H. 1972. Tetrodotoxin, saxitoxin and related substances: Their application in neurobiology.Int. Rev. Neurobiol. 5:83Google Scholar
  9. Henderson, R., Ritchie, J.M., Strichartz, G.R. 1974. Evidence that tetrodotoxin and saxitoxin act at a metal cation binding site in the sodium channels of nerve membrane.Proc. Nat. Acad. Sci. USA 71:3936Google Scholar
  10. Henderson, R., Wang, J.H. 1972. Solubilization of a specific tetrodotoxin-binding component from garfish olfactory nerve membrane.Biochemistry 11:4565Google Scholar
  11. Hille, B. 1968. Pharmacological modifications of the sodium channels of frog nerve.J. Gen. Physiol. 51:199Google Scholar
  12. Hodgkin, A.L., Huxley, A.F. 1952. A quantatitive description of membrane current and its application to conduction and excitation in nerve.J. Physiol. (London) 117:500Google Scholar
  13. Kao, C.Y. 1966. Tetrodotoxin, saxitoxin, and their significance in the study of excitation phenomena.Pharmacol. Rev. 18:997Google Scholar
  14. Keynes, R.D., Rojas, E. 1975. Kinetics and steady state properties of the charged system controlling sodium conductance in the squid giant axon.J. Physiol. (London) 239:393Google Scholar
  15. Levinson, S.R. 1975. The purity of tritiated tetrodotoxin as determined by bioassay.Philos. Trans. R. Soc. (London) B. 270:337Google Scholar
  16. Levinson, S.R., Meves, H. 1975. The binding of tritiated tetrodotoxin to squid giant axons.Philos. Trans. R. Soc. (London) B. 270:349Google Scholar
  17. Ritchie, J.M., Rogart, R.B. 1977a. The binding of saxitoxin and tetrodotoxin to excitable membranes.Rev. Physiol. Biochem. Pharmacol. 79:1Google Scholar
  18. Ritchie, J.M., Rogart, R.B. 1977b. The binding of labelled saxitoxin to the sodium channels in normal and denervated mammalian muscle, and in amphibian muscle.J. Physiol. (London) 269:341Google Scholar
  19. Ritchie, J.M., Rogart, R.B., Strichartz, G. 1976. A new method for labelling saxitoxin and its binding to non-myelinated fibres of the rabbit vagus, lobster walking leg, and garfish olfactory nerves.J. Physiol. (London) 261:477Google Scholar
  20. Spalding, B.C. 1978. Removal of TTX sensitivity in muscle fibers by trimethloxonium ion: Two acid groups at the sodium channel.Biophys. J. 21:41aGoogle Scholar
  21. Strichartz, G.R., Tang, C.M., Orkand, R.K. 1979. Sodium channels in axons and glial cells of mudpuppy optic nerve.Biophys. J. 25:66aGoogle Scholar
  22. Taylor, R.E. 1959. Effect of procaine on electrical properties of squid axon membrane.Am J. Physiol. 196:1071Google Scholar
  23. Villegas, J., Sevcik, C., Barnola, F.V., Villegas, R. 1976. Grayanotoxin, veratridine and tetrodotoxin-sensitive sodium pathways in the Schwann cell membrane of squid nerve fibers.J. Gen. Physiol. 67:369Google Scholar
  24. Yeh, J., Narahashi, T. 1974. Noncholinergic mechanism of action of cholinergic drugs on squid axon membranes.J. Pharmacol. Exp. Ther. 189:697Google Scholar

Copyright information

© Springer-Verlag New York Inc 1979

Authors and Affiliations

  • G. R. Strichartz
    • 1
    • 2
    • 3
  • R. B. Rogart
    • 1
    • 2
    • 3
  • J. M. Ritchie
    • 1
    • 2
    • 3
  1. 1.Department of Physiology and BiophysicsState University of New YorkStony Brook
  2. 2.Department of PharmacologyYale University, School of MedicineNew Haven
  3. 3.Marine Biological LaboratoryWoods Hole

Personalised recommendations