The Journal of Membrane Biology

, Volume 61, Issue 1, pp 31–38 | Cite as

A K+-selective, three-state channel from fragmented sarcoplasmic reticulum of frog leg muscle

  • Pedro P. Labarca
  • Christopher Miller
  • Pedro P. Labarca
    • 1
  • Christopher Miller
    • 1
  1. 1.Graduate Program in Biophysics and Graduate Department of BiochemistryBrandeis UniversityWaltham


Sarcoplasmic reticulum (SR) vesicles from frog leg muscle were fused with a planar phospholipid bilayer by a method described previously for rabbit SR. As a result of the fusion, K+-selective conduction channels are inserted into the bilayer. Unlike the two-state rabbit channel, the frog channel displays three states: a nonconducting (“closed”) state and two conducting states “α” and “β”. In 0.1m K+ the single-channel conductances are 50 and 150 pS for α and β, respectively. The probabilities of appearearance of the three states are voltage-dependent, and transitions between the closed and β states proceed through the α state. Both open states follow a quantitatively identical selectivity sequence in channel conductance: K+>NH 4 + >Rb+>Na+>Li+>Cs+. Both open states are blocked by Cs+ asymmetrically in a voltage-dependent manner. The zero-voltage dissociation constant for blocking is the same for both open states, but the voltage-dependences of the Cs+ block for the two states differ in a way suggesting that the Cs+ blocking site is located more deeply inside the membrane in the β than in the α state.

Key words

Sarcoplasmic reticulum K-channel, planar bilayer ion selectivity Cs-block excitation-contraction coupling 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Batra, S. 1973. The effects of zinc and lanthanum on calcium uptake in mitchondria and fragmented sarcoplasmic reticulum of frog skeletal muscle.J. Cell. Physiol. 82:245–256Google Scholar
  2. 2.
    Bezanilla, F., Horowicz, P. 1973. Fluorescence intensity changes associated with contractile activation in frog muscle stained with Nile blue A.J. Physiol. (London) 246:709–735Google Scholar
  3. 3.
    Caputo, C. 1978. Excitation and contraction processes in muscle.Annu. Rev. Biophys. Bioeng. 7:63–83Google Scholar
  4. 4.
    Cohen, F., Zimmerberg, J., Finkelstein, A. 1980. Fusion of phospholiqid vesicles with planar bilayers.J. Gen. Physiol. 75:251–270Google Scholar
  5. 5.
    Colombini, M. 1979. A candidate for the permeability pathway of the outer mitochondrial membrane.Nature (London) 279:643–645Google Scholar
  6. 6.
    Coronado, R. 1980. Ion Conduction and Selectivity in a Potassium Channel from Sarcoplasmic Reticulum. Ph.D. Thesis, Brandeis University, Waltham, Mass.Google Scholar
  7. 7.
    Coronado, R., Miller, C. 1979. Voltage dependent Cs+ block of a K+ channel from sarcoplasmic reticulum.Nature (London) 280:807–810Google Scholar
  8. 8.
    Coronado, R., Rosenberg, R., Miller, C. 1980. Ionic selectivity, saturation and block in a K+ selective channel from the sarcoplasmic reticulum.J. Gen. Physiol. 76:425–446Google Scholar
  9. 9.
    Endo, M. 1977. Calcium release from the sarcoplasmic reticulum.Physiol. Rev. 57:71–108Google Scholar
  10. 10.
    Kometani, T., Kasai, M. 1978. Ionic permeability of sarcoplasmic reticulum vesicles measured by light scattering method.J. Membrane Biol. 41:295–308Google Scholar
  11. 11.
    Labarca, P., Coronado, R., Miller, C. 1980. Thermodynamic and kinetic studies of the gating behavior of a K+ selective channel from sarcoplasmic reticulum.J. Gen. Physiol. 76:397–424Google Scholar
  12. 12.
    Latorre, R., Alvarez, A. 1981. Voltage-dependent channels in planar lipid bilayer membranes.Physiol. Rev. 61:77–150Google Scholar
  13. 13.
    Mathias, R.T., Levis, R.A., Eisenberg, R.S. 1980. Electrical models of excitation-contraction coupling and charge movement in skeletal muscle.J. Gen. Physiol. 76:1–32Google Scholar
  14. 14.
    McKinley, D., Meissner, G. 1978. Evidence for K+, Na+ permeable channel in sarcoplasmic reticulum.J. Membrane Biol. 44:159–186Google Scholar
  15. 15.
    Miller, C. 1978. Voltage-gated cation conductance channel from fragmented sarcoplasmic reticulum: Steady-state electrical properties.J. Membrane Biol. 40:1–23Google Scholar
  16. 16.
    Miller, C., Rosenberg, R. 1979. Modification of a voltagegated K+ channel from sarcoplasmic reticulum by a pronasederived specific endopeptidase.J. Gen. Physiol. 74:457–478Google Scholar
  17. 17.
    Mueller, P., Rudin, D.O. 1969. Bimolecular lipid membranes: Techniques of formation, study of electrical properties and induction of gating phenomena.In: Laboratory Techniques in Membrane Biophysics. H. Passow and R. Stampfli, editors. pp. 141–156. Springer-Verlag, BerlinGoogle Scholar
  18. 18.
    Peachey, L.D., Adrian, R.H. 1973. Electrical properties of the transverse tubular system.In: The Structure and Function of Muscle. G.H. Bourne, editor. Vol. III, pp. 1–29. Academic Press, New YorkGoogle Scholar
  19. 19.
    Vergara, J., Bezanilla, F., Salzberg, B.M. 1978. Nile blue fluorescence signals from cut single fibers under voltage clamp conditions.J. Gen. Physiol. 72:775–800Google Scholar

Copyright information

© Springer-Verlag New York Inc. 1981

Personalised recommendations

A K+-selective, three-state channel from fragmented sarcoplasmic reticulum of frog leg muscle