Voltage-controlled gating in a large conductance Ca2+-sensitive K+channel (hslo).
Large conductance calcium- and voltage-sensitive K+ (MaxiK) channels share properties of voltage- and ligand-gated ion channels. In voltage-gated channels, membrane depolarization promotes the displacement of charged residues contained in the voltage sensor (S4 region) inducing gating currents and pore opening. In MaxiK channels, both voltage and micromolar internal Ca2+ favor pore opening. We demonstrate the presence of voltage sensor rearrangements with voltage (gating currents) whose movement and associated pore opening is triggered by voltage and facilitated by micromolar internal Ca2+ concentration. In contrast to other voltage-gated channels, in MaxiK channels there is charge movement at potentials where the pore is open and the total charge per channel is 4-5 elementary charges.
Stefani
E
E
Department of Anesthesiology, University of California, Los Angeles, CA 90095, USA.
Ottolia
M
M
Noceti
F
F
Olcese
R
R
Wallner
M
M
Latorre
R
R
Toro
L
L
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002586:Cesium / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000096:biosynthesis / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D011336:Probability; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014982:Xenopus laevis
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D011994:Recombinant Proteins; D051637:Shaker Superfamily of Potassium Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D019789:Tetraethylammonium; D002118:Calcium