The multi-ion nature of the pore in Shaker K+ channels
Autor: | Ted Begenisich, Patricia Pérez-Cornejo |
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Rok vydání: | 1994 |
Předmět: |
Cell Membrane Permeability
Potassium Channels Biophysics Analytical chemistry Cesium Ionic bonding chemistry.chemical_element Moths Models Biological Cell Line Membrane Potentials Rubidium Ion Ammonia Animals Patch clamp Shaker Membrane potential Chemistry Permeation Electric Stimulation Recombinant Proteins Potassium channel Kinetics Potassium Drosophila Baculoviridae Mathematics Research Article |
Zdroj: | Scopus-Elsevier |
ISSN: | 0006-3495 |
Popis: | We have investigated some of the permeation properties of the pore in Shaker K channels. We determined the apparent permeability ratio of K+, Rb+, and NH4+ ions and block of the pore by external Cs+ ions. Shaker channels were expressed with the baculovirus/Sf9 expression system and the channel currents measured with the whole-cell variant of the patch clamp technique. The apparent permeability ratio, PRb/PK, determined in biionic conditions with internal K+, was a function of external Rb+ concentration. A large change in PRb/PK occurred with reversed ionic conditions (internal Rb+ and external K+). These changes in apparent permeability were not due to differences in membrane potential. With internal K+, PNH4/PK was not a function of external NH4+ concentration (at least over the range 50-120 mM). We also investigated block of the pore by external Cs+ ions. At a concentration of 20 mM, Cs+ block had a voltage dependence equivalent to that of an ion with a valence of 0.91; this increased to 1.3 at 40 mM Cs+. We show that a 4-barrier, 3-site permeation model can simulate these and many of the other known properties of ion permeation in Shaker channels. |
Databáze: | OpenAIRE |
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