Steady-state and closed-state inactivation properties of inactivating BK channels

Jiu Ping Ding, Christopher J. Lingle

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Calcium-dependent potassium (BK-type) Ca2+ and voltage-dependent K+ channels in chromaffin cells exhibit an inactivation that probably arises from coassembly of Slo1 α subunits with auxiliary β subunits. One goal of this work was to determine whether the Ca2+ dependence of inactivation arises from any mechanism other than coupling of inactivation to the Ca2+ dependence of activation. Steady-state inactivation and the onset of inactivation were studied in inside-out patches and whole-cell recordings from rat adrenal chromaffin cells with parallel experiments on inactivating BK channels resulting from cloned α + β2 subunits. In both cases, steady-state inactivation was shifted to more negative potentials by increases in submembrane [Ca2+] from 1 to 60 μM. At 10 and 60 μM Ca2+, the maximal channel availability at negative potentials was similar despite a shift in the voltage of half availability, suggesting there is no strictly Ca2+-dependent inactivation. In contrast, in the absence of Ca2+, depolarization to potentials positive to +20 mV induces channel inactivation. Thus, voltage-dependent, but not solely Ca2+-dependent, kinetic steps are required for inactivation to occur. Finally, under some conditions, BK channels are shown to inactivate as readily from closed states as from open states, indicative that a key conformational change required for inactivation precedes channel opening.

Original languageEnglish
Pages (from-to)2448-2465
Number of pages18
JournalBiophysical Journal
Issue number5
StatePublished - 2002


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