Department of Anesthesiology

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Ca2+-dependent gating mechanisms for dSlo, a large-conductance Ca2+-activated K+ (BK) channel.

TitleCa2+-dependent gating mechanisms for dSlo, a large-conductance Ca2+-activated K+ (BK) channel.
Publication TypeJournal Article
Year of Publication1999
AuthorsMoss BL, Silberberg SD, Nimigean CM, Magleby KL
JournalBiophys J
Volume76
Issue6
Pagination3099-117
Date Published1999 Jun
ISSN0006-3495
KeywordsAnimals, Biophysical Phenomena, Biophysics, Calcium, Drosophila, Drosophila Proteins, Female, Genetic Variation, Ion Channel Gating, Kinetics, Large-Conductance Calcium-Activated Potassium Channels, Models, Biological, Oocytes, Point Mutation, Potassium Channels, Potassium Channels, Calcium-Activated, Rats, Recombinant Proteins, Xenopus laevis
Abstract

The Ca2+-dependent gating mechanism of cloned BK channels from Drosophila (dSlo) was studied. Both a natural variant (A1/C2/E1/G3/IO) and a mutant (S942A) were expressed in Xenopus oocytes, and single-channel currents were recorded from excised patches of membrane. Stability plots were used to define stable segments of data. Unlike native BK channels from rat skeletal muscle in which increasing internal Ca2+ concentration (Cai2+) in the range of 5 to 30 microM increases mean open time, increasing Cai2+ in this range for dSlo had little effect on mean open time. However, further increases in Cai2+ to 300 or 3000 microM then typically increased dSlo mean open time. Kinetic schemes for the observed Ca2+-dependent gating kinetics of dSlo were evaluated by fitting two-dimensional dwell-time distributions using maximum likelihood techniques and by comparing observed dependency plots with those predicted by the models. Previously described kinetic schemes that largely account for the Ca2+-dependent kinetics of native BK channels from rat skeletal muscle did not adequately describe the Ca2+ dependence of dSlo. An expanded version of these schemes which, in addition to the Ca2+-activation steps, permitted a Ca2+-facilitated transition from each open state to a closed state, could approximate the Ca2+-dependent kinetics of dSlo, suggesting that Ca2+ may exert dual effects on gating.

DOI10.1016/S0006-3495(99)77462-X
Alternate JournalBiophys. J.
PubMed ID10354435
PubMed Central IDPMC1300279
Grant ListAR32805 / AR / NIAMS NIH HHS / United States
NS007044 / NS / NINDS NIH HHS / United States
NS30584 / NS / NINDS NIH HHS / United States