PMID: 9450947Mar 7, 1998Paper

Time-irreversible subconductance gating associated with Ba2+ block of large conductance Ca2+-activated K+ channels

The Journal of General Physiology
R A Bello, K L Magleby

Abstract

Ba2+ block of large conductance Ca2+-activated K+ channels was studied in patches of membrane excised from cultures of rat skeletal muscle using the patch clamp technique. Under conditions in which a blocking Ba2+ ion would dissociate to the external solution (150 mM N-methyl-D-glucamine+o, 500 mM K+i, 10 microM Ba2+i, +30 mV, and 100 microM Ca2+i to fully activate the channel), Ba2+ blocks with a mean duration of approximately 2 s occurred, on average, once every approximately 100 ms of channel open time. Of these Ba2+ blocks, 78% terminated with a single step in the current to the fully open level and 22% terminated with a transition to a subconductance level at approximately 0.26 of the fully open level (preopening) before stepping to the fully open level. Only one apparent preclosing was observed in approximately 10,000 Ba2+ blocks. Thus, the preopenings represent Ba2+-induced time-irreversible subconductance gating. The fraction of Ba2+ blocks terminating with a preopening and the duration of preopenings (exponentially distributed, mean = 0.75 ms) appeared independent of changes in [Ba2+]i or membrane potential. The fractional conductance of the preopenings increased from 0.24 at +10 mV to 0.39 at +90 mV. In contrast, the ...Continue Reading

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Citations

Jun 27, 2012·Proceedings of the National Academy of Sciences of the United States of America·Yu ZhouChristopher J Lingle
Apr 28, 2010·The Journal of General Physiology·Christopher ShelleyKarl L Magleby
Oct 13, 2010·The Journal of General Physiology·Andrew S Thomson, Brad S Rothberg
Mar 30, 2004·The Journal of Physiology·Xiao-Ping SunAlan D Grinnell
Oct 25, 2006·Molecular Membrane Biology·Heidi De WetRichard Callaghan
Jan 5, 2002·Canadian Journal of Physiology and Pharmacology·T J HawkeM I Lindinger
Feb 5, 2002·Canadian Journal of Physiology and Pharmacology·M I LindingerS L Lipskie
Jul 30, 2008·The Journal of Physical Chemistry. B·Kee-Hyun ChoiStuart Licht

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