Skip to main content
NCBI home page
The Journal of General Physiology logoLink to The Journal of General Physiology
. 1994 Mar 1;103(3):447–470. doi: 10.1085/jgp.103.3.447

Ion permeation, divalent ion block, and chemical modification of single sodium channels. Description by single- and double-occupancy rate- theory models [published erratum appears in J Gen Physiol 1994 May;103(5):937]

PMCID: PMC2216843  PMID: 8037798

Abstract

Calcium ions, applied internally, externally, or symmetrically, have been used in conjunction with rate-theory modeling to explore the energy profile of the ion-conducting pore of sodium channels. The block, by extracellular and/or intracellular calcium, of sodium ion conduction through single, batrachotoxin-activated sodium channels from rat brain was studied in planar lipid bilayers. Extracellular calcium caused a reduction of inward current that was enhanced by hyperpolarization and a weaker block of outward current. Intracellular calcium reduced both outward and inward sodium current, with the block being weakly dependent on voltage and enhanced by depolarization. These results, together with the dependence of single-channel conductance on sodium concentration, and the effects of symmetrically applied calcium, were described using single- or double-occupancy, three-barrier, two- site (3B2S), or single-occupancy, 4B3S rate-theory models. There appear to be distinct outer and inner regions of the channel, easily accessed by external or internal calcium respectively, separated by a rate- limiting barrier to calcium permeation. Most of the data could be well fit by each of the models. Reducing the ion interaction energies sufficiently to allow a small but significant probability of two-ion occupancy in the 3B2S model yielded better overall fits than for either 3B2S or 4B3S models constrained to single occupancy. The outer ion- binding site of the model may represent a section of the pore in which sodium, calcium, and guanidinium toxins, such as saxitoxin or tetrodotoxin, compete. Under physiological conditions, with millimolar calcium externally, and high potassium internally, the model channels are occupied by calcium or potassium much of the time, causing a significant reduction in single-channel conductance from the value measured with sodium as the only cation species present. Sodium conductance and degree of block by external calcium are reduced by modification of single channels with the carboxyl reagent, trimethyloxonium (TMO) (Worley et al., 1986) Journal of General Physiology. 87:327-349). Elevations of only the outermost parts of the energy profiles for sodium and calcium were sufficient to account for the reductions in conductance and in efficacy of calcium block produced by TMO modification.

Full Text

The Full Text of this article is available as a PDF (1.4 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Albitz R., Magyar J., Nilius B. Block of single cardiac sodium channels by intracellular magnesium. Eur Biophys J. 1990;19(1):19–23. doi: 10.1007/BF00223569. [DOI] [PubMed] [Google Scholar]
  2. Alvarez O., Villarroel A., Eisenman G. Calculation of ion currents from energy profiles and energy profiles from ion currents in multibarrier, multisite, multioccupancy channel model. Methods Enzymol. 1992;207:816–854. doi: 10.1016/0076-6879(92)07058-v. [DOI] [PubMed] [Google Scholar]
  3. Baker P. F., Hodgkin A. L., Ridgway E. B. Depolarization and calcium entry in squid giant axons. J Physiol. 1971 Nov;218(3):709–755. doi: 10.1113/jphysiol.1971.sp009641. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Becker S., Prusak-Sochaczewski E., Zamponi G., Beck-Sickinger A. G., Gordon R. D., French R. J. Action of derivatives of mu-conotoxin GIIIA on sodium channels. Single amino acid substitutions in the toxin separately affect association and dissociation rates. Biochemistry. 1992 Sep 8;31(35):8229–8238. doi: 10.1021/bi00150a016. [DOI] [PubMed] [Google Scholar]
  5. Begenisich T. B., Cahalan M. D. Sodium channel permeation in squid axons. I: Reversal potential experiments. J Physiol. 1980 Oct;307:217–242. doi: 10.1113/jphysiol.1980.sp013432. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Begenisich T. B., Cahalan M. D. Sodium channel permeation in squid axons. II: Non-independence and current-voltage relations. J Physiol. 1980 Oct;307:243–257. doi: 10.1113/jphysiol.1980.sp013433. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Begenisich T., Busath D. Sodium flux ratio in voltage-clamped squid giant axons. J Gen Physiol. 1981 May;77(5):489–502. doi: 10.1085/jgp.77.5.489. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Begenisich T., Danko M. Hydrogen ion block of the sodium pore in squid giant axons. J Gen Physiol. 1983 Nov;82(5):599–618. doi: 10.1085/jgp.82.5.599. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Busath D., Begenisich T. Unidirectional sodium and potassium fluxes through the sodium channel of squid giant axons. Biophys J. 1982 Oct;40(1):41–49. doi: 10.1016/S0006-3495(82)84456-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Butler J. N. The thermodynamic activity of calcium ion in sodium chloride-calcium chloride electrolytes. Biophys J. 1968 Dec;8(12):1426–1433. doi: 10.1016/S0006-3495(68)86564-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Cahalan M., Begenisich T. Sodium channel selectivity. Dependence on internal permeant ion concentration. J Gen Physiol. 1976 Aug;68(2):111–125. doi: 10.1085/jgp.68.2.111. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Cai M., Jordan P. C. How does vestibule surface charge affect ion conduction and toxin binding in a sodium channel? Biophys J. 1990 Apr;57(4):883–891. doi: 10.1016/S0006-3495(90)82608-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Castillo C., Villegas R., Recio-Pinto E. Alkaloid-modified sodium channels from lobster walking leg nerves in planar lipid bilayers. J Gen Physiol. 1992 Jun;99(6):897–930. doi: 10.1085/jgp.99.6.897. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Chabala L. D., Andersen O. S. Carbodiimide modification reduces the conductance and increases the tetrodotoxin sensitivity in batrachotoxin-modified sodium channels. Pflugers Arch. 1992 Jun;421(2-3):262–269. doi: 10.1007/BF00374836. [DOI] [PubMed] [Google Scholar]
  15. Chahine M., Chen L. Q., Kallen R. G., Barchi R. L., Horn R. Expressed Na channel clones differ in their sensitivity to external calcium concentration. Biophys J. 1992 Apr;62(1):37–40. doi: 10.1016/S0006-3495(92)81771-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Cooper K. E., Gates P. Y., Eisenberg R. S. Diffusion theory and discrete rate constants in ion permeation. J Membr Biol. 1988 Dec;106(2):95–105. doi: 10.1007/BF01871391. [DOI] [PubMed] [Google Scholar]
  17. Correa A. M., Latorre R., Bezanilla F. Ion permeation in normal and batrachotoxin-modified Na+ channels in the squid giant axon. J Gen Physiol. 1991 Mar;97(3):605–625. doi: 10.1085/jgp.97.3.605. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Cukierman S., Krueger B. K. Modulation of sodium channel gating by external divalent cations: differential effects on opening and closing rates. Pflugers Arch. 1990 Jun;416(4):360–367. doi: 10.1007/BF00370741. [DOI] [PubMed] [Google Scholar]
  19. Dani J. A. Ion-channel entrances influence permeation. Net charge, size, shape, and binding considerations. Biophys J. 1986 Mar;49(3):607–618. doi: 10.1016/S0006-3495(86)83688-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Daumas P., Andersen O. S. Proton block of rat brain sodium channels. Evidence for two proton binding sites and multiple occupancy. J Gen Physiol. 1993 Jan;101(1):27–43. doi: 10.1085/jgp.101.1.27. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Dudley S. C., Jr, Baumgarten C. M. Modification of cardiac sodium channels by carboxyl reagents. Trimethyloxonium and water-soluble carbodiimide. J Gen Physiol. 1993 May;101(5):651–671. doi: 10.1085/jgp.101.5.651. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Ebert G. A., Goldman L. The permeability of the sodium channel in Myxicola to the alkali cations. J Gen Physiol. 1976 Sep;68(3):327–340. doi: 10.1085/jgp.68.3.327. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. French R. J., Shoukimas J. J. An ion's view of the potassium channel. The structure of the permeation pathway as sensed by a variety of blocking ions. J Gen Physiol. 1985 May;85(5):669–698. doi: 10.1085/jgp.85.5.669. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. French R. J., Wells J. B. Sodium ions as blocking agents and charge carriers in the potassium channel of the squid giant axon. J Gen Physiol. 1977 Dec;70(6):707–724. doi: 10.1085/jgp.70.6.707. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. French R. J., Worley J. F., 3rd, Krueger B. K. Voltage-dependent block by saxitoxin of sodium channels incorporated into planar lipid bilayers. Biophys J. 1984 Jan;45(1):301–310. doi: 10.1016/S0006-3495(84)84156-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Garber S. S., Miller C. Single Na+ channels activated by veratridine and batrachotoxin. J Gen Physiol. 1987 Mar;89(3):459–480. doi: 10.1085/jgp.89.3.459. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Garber S. S. Symmetry and asymmetry of permeation through toxin-modified Na+ channels. Biophys J. 1988 Nov;54(5):767–776. doi: 10.1016/S0006-3495(88)83014-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Green W. N., Andersen O. S. Surface charges and ion channel function. Annu Rev Physiol. 1991;53:341–359. doi: 10.1146/annurev.ph.53.030191.002013. [DOI] [PubMed] [Google Scholar]
  29. Green W. N., Weiss L. B., Andersen O. S. Batrachotoxin-modified sodium channels in planar lipid bilayers. Characterization of saxitoxin- and tetrodotoxin-induced channel closures. J Gen Physiol. 1987 Jun;89(6):873–903. doi: 10.1085/jgp.89.6.873. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Green W. N., Weiss L. B., Andersen O. S. Batrachotoxin-modified sodium channels in planar lipid bilayers. Ion permeation and block. J Gen Physiol. 1987 Jun;89(6):841–872. doi: 10.1085/jgp.89.6.841. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. HODGKIN A. L., HUXLEY A. F. Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):449–472. doi: 10.1113/jphysiol.1952.sp004717. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. HODGKIN A. L., KATZ B. The effect of sodium ions on the electrical activity of giant axon of the squid. J Physiol. 1949 Mar 1;108(1):37–77. doi: 10.1113/jphysiol.1949.sp004310. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. HODGKIN A. L., KEYNES R. D. The potassium permeability of a giant nerve fibre. J Physiol. 1955 Apr 28;128(1):61–88. doi: 10.1113/jphysiol.1955.sp005291. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Heginbotham L., MacKinnon R. The aromatic binding site for tetraethylammonium ion on potassium channels. Neuron. 1992 Mar;8(3):483–491. doi: 10.1016/0896-6273(92)90276-j. [DOI] [PubMed] [Google Scholar]
  35. Heinemann S. H., Terlau H., Stühmer W., Imoto K., Numa S. Calcium channel characteristics conferred on the sodium channel by single mutations. Nature. 1992 Apr 2;356(6368):441–443. doi: 10.1038/356441a0. [DOI] [PubMed] [Google Scholar]
  36. Hille B. Ionic selectivity of Na and K channels of nerve membranes. Membranes. 1975;3:255–323. [PubMed] [Google Scholar]
  37. Hille B. Ionic selectivity, saturation, and block in sodium channels. A four-barrier model. J Gen Physiol. 1975 Nov;66(5):535–560. doi: 10.1085/jgp.66.5.535. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Krueger B. K., Worley J. F., 3rd, French R. J. Block of sodium channels in planar lipid bilayers by guanidium toxins and calcium. Are the mechanisms of voltage dependence the same? Ann N Y Acad Sci. 1986;479:257–268. doi: 10.1111/j.1749-6632.1986.tb15574.x. [DOI] [PubMed] [Google Scholar]
  39. Krueger B. K., Worley J. F., 3rd, French R. J. Single sodium channels from rat brain incorporated into planar lipid bilayer membranes. Nature. 1983 May 12;303(5913):172–175. doi: 10.1038/303172a0. [DOI] [PubMed] [Google Scholar]
  40. Levitt D. G. Exact continuum solution for a channel that can be occupied by two ions. Biophys J. 1987 Sep;52(3):455–466. doi: 10.1016/S0006-3495(87)83234-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Lin F., Conti F., Moran O. Competitive blockage of the sodium channel by intracellular magnesium ions in central mammalian neurones. Eur Biophys J. 1991;19(3):109–118. doi: 10.1007/BF00185451. [DOI] [PubMed] [Google Scholar]
  42. MacKinnon R., Miller C. Mutant potassium channels with altered binding of charybdotoxin, a pore-blocking peptide inhibitor. Science. 1989 Sep 22;245(4924):1382–1385. doi: 10.1126/science.2476850. [DOI] [PubMed] [Google Scholar]
  43. Meves H., Vogel W. Calcium inward currents in internally perfused giant axons. J Physiol. 1973 Nov;235(1):225–265. doi: 10.1113/jphysiol.1973.sp010386. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Moczydlowski E., Garber S. S., Miller C. Batrachotoxin-activated Na+ channels in planar lipid bilayers. Competition of tetrodotoxin block by Na+. J Gen Physiol. 1984 Nov;84(5):665–686. doi: 10.1085/jgp.84.5.665. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Moczydlowski E., Hall S., Garber S. S., Strichartz G. S., Miller C. Voltage-dependent blockade of muscle Na+ channels by guanidinium toxins. J Gen Physiol. 1984 Nov;84(5):687–704. doi: 10.1085/jgp.84.5.687. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Moczydlowski E. Profiles of permeation through Na-channels. Biophys J. 1993 Apr;64(4):1051–1052. doi: 10.1016/S0006-3495(93)81459-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  47. Moczydlowski E., Uehara A., Guo X., Heiny J. Isochannels and blocking modes of voltage-dependent sodium channels. Ann N Y Acad Sci. 1986;479:269–292. doi: 10.1111/j.1749-6632.1986.tb15575.x. [DOI] [PubMed] [Google Scholar]
  48. Naranjo D., Latorre R. Ion conduction in substates of the batrachotoxin-modified Na+ channel from toad skeletal muscle. Biophys J. 1993 Apr;64(4):1038–1050. doi: 10.1016/S0006-3495(93)81469-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Noda M., Suzuki H., Numa S., Stühmer W. A single point mutation confers tetrodotoxin and saxitoxin insensitivity on the sodium channel II. FEBS Lett. 1989 Dec 18;259(1):213–216. doi: 10.1016/0014-5793(89)81531-5. [DOI] [PubMed] [Google Scholar]
  50. Park C. S., Miller C. Interaction of charybdotoxin with permeant ions inside the pore of a K+ channel. Neuron. 1992 Aug;9(2):307–313. doi: 10.1016/0896-6273(92)90169-e. [DOI] [PubMed] [Google Scholar]
  51. Ravindran A., Kwiecinski H., Alvarez O., Eisenman G., Moczydlowski E. Modeling ion permeation through batrachotoxin-modified Na+ channels from rat skeletal muscle with a multi-ion pore. Biophys J. 1992 Feb;61(2):494–508. doi: 10.1016/S0006-3495(92)81854-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Ravindran A., Moczydlowski E. Influence of negative surface charge on toxin binding to canine heart Na channels in planar bilayers. Biophys J. 1989 Feb;55(2):359–365. doi: 10.1016/S0006-3495(89)82813-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  53. Recio-Pinto E., Duch D. S., Levinson S. R., Urban B. W. Purified and unpurified sodium channels from eel electroplax in planar lipid bilayers. J Gen Physiol. 1987 Sep;90(3):375–395. doi: 10.1085/jgp.90.3.375. [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Terlau H., Heinemann S. H., Stühmer W., Pusch M., Conti F., Imoto K., Numa S. Mapping the site of block by tetrodotoxin and saxitoxin of sodium channel II. FEBS Lett. 1991 Nov 18;293(1-2):93–96. doi: 10.1016/0014-5793(91)81159-6. [DOI] [PubMed] [Google Scholar]
  55. Wagoner P. K., Oxford G. S. Cation permeation through the voltage-dependent potassium channel in the squid axon. Characteristics and mechanisms. J Gen Physiol. 1987 Aug;90(2):261–290. doi: 10.1085/jgp.90.2.261. [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Woodhull A. M. Ionic blockage of sodium channels in nerve. J Gen Physiol. 1973 Jun;61(6):687–708. doi: 10.1085/jgp.61.6.687. [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Worley J. F., 3rd, French R. J., Krueger B. K. Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium. J Gen Physiol. 1986 Feb;87(2):327–349. doi: 10.1085/jgp.87.2.327. [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Worley J. F., 3rd, French R. J., Pailthorpe B. A., Krueger B. K. Lipid surface charge does not influence conductance or calcium block of single sodium channels in planar bilayers. Biophys J. 1992 May;61(5):1353–1363. doi: 10.1016/S0006-3495(92)81942-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Wu J. V. Dynamic ion-ion and water-ion interactions in ion channels. Biophys J. 1992 May;61(5):1316–1331. doi: 10.1016/S0006-3495(92)81940-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Yamamoto D., Yeh J. Z., Narahashi T. Voltage-dependent calcium block of normal and tetramethrin-modified single sodium channels. Biophys J. 1984 Jan;45(1):337–344. doi: 10.1016/S0006-3495(84)84159-4. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of General Physiology are provided here courtesy of The Rockefeller University Press

RESOURCES