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. 1991 Jan 1;97(1):117–142. doi: 10.1085/jgp.97.1.117

Zn2(+)-induced subconductance events in cardiac Na+ channels prolonged by batrachotoxin. Current-voltage behavior and single-channel kinetics

PMCID: PMC2216469  PMID: 1848882

Abstract

The mechanism of voltage-dependent substate production by external Zn2+ in batrachotoxin-modified Na+ channels from canine heart was investigated by analysis of the current-voltage behavior and single- channel kinetics of substate events. At the single-channel level the addition of external Zn2+ results in an increasing frequency of substate events with a mean duration of approximately 15-25 ms for the substate dwell time observed in the range of -70 to +70 mV. Under conditions of symmetrical 0.2 M NaCl, the open state of cardiac Na+ channels displays ohmic current-voltage behavior in the range of -90 to +100 mV, with a slope conductance of 21 pS. In contrast, the Zn2(+)- induced substate exhibits significant outward rectification with a slope conductance of 3.1 pS in the range of -100 to -50 mV and 5.1 pS in the range of +50 to +100 mV. Analysis of dwell-time histograms of substate events as a function of Zn2+ concentration and voltage led to the consideration of two types of models that may explain this behavior. Using a simple one-site blocking model, the apparent association rate for Zn2+ binding is more strongly voltage dependent (decreasing e-fold per +60 mV) than the Zn2+ dissociation rate (increasing e-fold per +420 mV). However, this simple blocking model cannot account for the dependence of the apparent dissociation rate on Zn2+ concentration. To explain this result, a four-state kinetic scheme involving a Zn2(+)-induced conformational change from a high conductance conformation to a substate conformation is proposed. This model, similar to one introduced by Pietrobon et al. (1989. J. Gen. Physiol. 94:1-24) for H(+)-induced substate behavior in L-type Ca2+ channels, is able to simulate the kinetic and equilibrium behavior of the primary Zn2(+)-induced substate process in heart Na+ channels. This model implies that binding of Zn2+ greatly enhances conversion of the open, ohmic channel to a low conductance conformation with an asymmetric energy profile for Na+ permeation.

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Selected References

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  1. Behrens M. I., Oberhauser A., Bezanilla F., Latorre R. Batrachotoxin-modified sodium channels from squid optic nerve in planar bilayers. Ion conduction and gating properties. J Gen Physiol. 1989 Jan;93(1):23–41. doi: 10.1085/jgp.93.1.23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Blatz A. L., Magleby K. L. Correcting single channel data for missed events. Biophys J. 1986 May;49(5):967–980. doi: 10.1016/S0006-3495(86)83725-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Colquhoun D., Hawkes A. G. Relaxation and fluctuations of membrane currents that flow through drug-operated channels. Proc R Soc Lond B Biol Sci. 1977 Nov 14;199(1135):231–262. doi: 10.1098/rspb.1977.0137. [DOI] [PubMed] [Google Scholar]
  4. Frelin C., Cognard C., Vigne P., Lazdunski M. Tetrodotoxin-sensitive and tetrodotoxin-resistant Na+ channels differ in their sensitivity to Cd2+ and Zn2+. Eur J Pharmacol. 1986 Mar 18;122(2):245–250. doi: 10.1016/0014-2999(86)90109-3. [DOI] [PubMed] [Google Scholar]
  5. 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]
  6. Guo X. T., Uehara A., Ravindran A., Bryant S. H., Hall S., Moczydlowski E. Kinetic basis for insensitivity to tetrodotoxin and saxitoxin in sodium channels of canine heart and denervated rat skeletal muscle. Biochemistry. 1987 Dec 1;26(24):7546–7556. doi: 10.1021/bi00398a003. [DOI] [PubMed] [Google Scholar]
  7. Hartshorne R. P., Keller B. U., Talvenheimo J. A., Catterall W. A., Montal M. Functional reconstitution of the purified brain sodium channel in planar lipid bilayers. Proc Natl Acad Sci U S A. 1985 Jan;82(1):240–244. doi: 10.1073/pnas.82.1.240. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Huang L. Y., Moran N., Ehrenstein G. Gating kinetics of batrachotoxin-modified sodium channels in neuroblastoma cells determined from single-channel measurements. Biophys J. 1984 Jan;45(1):313–322. doi: 10.1016/S0006-3495(84)84157-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Keller B. U., Hartshorne R. P., Talvenheimo J. A., Catterall W. A., Montal M. Sodium channels in planar lipid bilayers. Channel gating kinetics of purified sodium channels modified by batrachotoxin. J Gen Physiol. 1986 Jul;88(1):1–23. doi: 10.1085/jgp.88.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Lansman J. B., Hess P., Tsien R. W. Blockade of current through single calcium channels by Cd2+, Mg2+, and Ca2+. Voltage and concentration dependence of calcium entry into the pore. J Gen Physiol. 1986 Sep;88(3):321–347. doi: 10.1085/jgp.88.3.321. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Lucchesi K., Moczydlowski E. Subconductance behavior in a maxi Ca2(+)-activated K+ channel induced by dendrotoxin-I. Neuron. 1990 Jan;4(1):141–148. doi: 10.1016/0896-6273(90)90450-t. [DOI] [PubMed] [Google Scholar]
  12. MONOD J., WYMAN J., CHANGEUX J. P. ON THE NATURE OF ALLOSTERIC TRANSITIONS: A PLAUSIBLE MODEL. J Mol Biol. 1965 May;12:88–118. doi: 10.1016/s0022-2836(65)80285-6. [DOI] [PubMed] [Google Scholar]
  13. Matsuda H., Matsuura H., Noma A. Triple-barrel structure of inwardly rectifying K+ channels revealed by Cs+ and Rb+ block in guinea-pig heart cells. J Physiol. 1989 Jun;413:139–157. doi: 10.1113/jphysiol.1989.sp017646. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Milne R. K., Yeo G. F., Madsen B. W., Edeson R. O. Estimation of single channel kinetic parameters from data subject to limited time resolution. Biophys J. 1989 Apr;55(4):673–676. doi: 10.1016/S0006-3495(89)82865-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. 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]
  16. 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]
  17. Neyton J., Miller C. Potassium blocks barium permeation through a calcium-activated potassium channel. J Gen Physiol. 1988 Nov;92(5):549–567. doi: 10.1085/jgp.92.5.549. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Patlak J. B. Sodium channel subconductance levels measured with a new variance-mean analysis. J Gen Physiol. 1988 Oct;92(4):413–430. doi: 10.1085/jgp.92.4.413. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Pietrobon D., Prod'hom B., Hess P. Conformational changes associated with ion permeation in L-type calcium channels. Nature. 1988 May 26;333(6171):373–376. doi: 10.1038/333373a0. [DOI] [PubMed] [Google Scholar]
  20. Pietrobon D., Prod'hom B., Hess P. Interactions of protons with single open L-type calcium channels. pH dependence of proton-induced current fluctuations with Cs+, K+, and Na+ as permeant ions. J Gen Physiol. 1989 Jul;94(1):1–21. doi: 10.1085/jgp.94.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Prod'hom B., Pietrobon D., Hess P. Direct measurement of proton transfer rates to a group controlling the dihydropyridine-sensitive Ca2+ channel. Nature. 1987 Sep 17;329(6136):243–246. doi: 10.1038/329243a0. [DOI] [PubMed] [Google Scholar]
  22. Prod'hom B., Pietrobon D., Hess P. Interactions of protons with single open L-type calcium channels. Location of protonation site and dependence of proton-induced current fluctuations on concentration and species of permeant ion. J Gen Physiol. 1989 Jul;94(1):23–42. doi: 10.1085/jgp.94.1.23. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. 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]
  24. Rogart R. B., Cribbs L. L., Muglia L. K., Kephart D. D., Kaiser M. W. Molecular cloning of a putative tetrodotoxin-resistant rat heart Na+ channel isoform. Proc Natl Acad Sci U S A. 1989 Oct;86(20):8170–8174. doi: 10.1073/pnas.86.20.8170. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Roux B., Sauvé R. A general solution to the time interval omission problem applied to single channel analysis. Biophys J. 1985 Jul;48(1):149–158. doi: 10.1016/S0006-3495(85)83768-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Sigworth F. J., Sine S. M. Data transformations for improved display and fitting of single-channel dwell time histograms. Biophys J. 1987 Dec;52(6):1047–1054. doi: 10.1016/S0006-3495(87)83298-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Tanabe T., Takeshima H., Mikami A., Flockerzi V., Takahashi H., Kangawa K., Kojima M., Matsuo H., Hirose T., Numa S. Primary structure of the receptor for calcium channel blockers from skeletal muscle. Nature. 1987 Jul 23;328(6128):313–318. doi: 10.1038/328313a0. [DOI] [PubMed] [Google Scholar]
  28. Trimmer J. S., Agnew W. S. Molecular diversity of voltage-sensitive Na channels. Annu Rev Physiol. 1989;51:401–418. doi: 10.1146/annurev.ph.51.030189.002153. [DOI] [PubMed] [Google Scholar]
  29. Vergara C., Latorre R. Kinetics of Ca2+-activated K+ channels from rabbit muscle incorporated into planar bilayers. Evidence for a Ca2+ and Ba2+ blockade. J Gen Physiol. 1983 Oct;82(4):543–568. doi: 10.1085/jgp.82.4.543. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. 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]
  31. 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]

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