A family of calcium-dependent potassium channels from rat brain.
By incorporating rat brain plasma membrane vesicles into planar lipid bilayers, we have found and characterized four types of Ca2(+)-activated K+ channels. The unitary conductances of these channels are 242 +/- 14 pS, 236 +/- 16 pS, 135 +/- 10 pS, and 76 +/- 6 pS in symmetrical 150 mM KCI buffers. These channels share a number of properties. They are all activated by depolarizing voltages, activated by micromolar concentrations of internal Ca2+ with a Hill coefficient for Ca2+ activation of between 2 and 3, noninactivating under our assay conditions, blocked by low millimolar concentrations of TEA from the outside, apamin-insensitive, and very selective for K+ over Na+ and Cl-. Three of the four channels are also blocked by nanomolar concentrations of charybdotoxin. One of the high conductance Ca2(+)-activated K+ channels is novel in that it is not blocked by charybdotoxin and exhibits gating kinetics highlighted by long closed times and long open times. This family of closely related Ca2(+)-activated K+ channels may share structural domains underlying particular functions.
Reinhart
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PH
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Chung
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S
Levitan
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D000818:Animals; D001921:Brain / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity; D007700:Kinetics; D008051:Lipid Bilayers; D008561:Membrane Fusion; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats
D008051:Lipid Bilayers; D015221:Potassium Channels; D002118:Calcium