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Voltage‐dependent inactivation of the human K + channel KvLQT1 is eliminated by association with minimal K + channel (minK) subunits
Author(s) -
TristaniFirouzi Martin,
Sanguinetti Michael C.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.037bz.x
Subject(s) - mink , gating , biophysics , depolarization , time constant , xenopus , patch clamp , potassium channel , chemistry , biology , electrophysiology , biochemistry , neuroscience , ecology , gene , electrical engineering , engineering
1 The time course and voltage dependence of inactivation of KvLQT1 channels expressed in Xenopus oocytes were studied using two‐microelectrode voltage‐clamp techniques. 2 Tail current analysis was used to characterize the kinetics of channel inactivation and deactivation. The time constant for recovery from channel inactivation was voltage dependent and varied from 30 ± 2 ms at −90 mV to 36 ± 1 ms at −30 mV. The time constant for deactivation varied from 186 ± 21 to 986 ± 43 ms over the same voltage range. 3 Inactivation of KvLQT1 channels was incomplete, reducing fully activated current by 35 % at +40 mV. Inactivation of KvLQT1 channels was half‐maximal at −18 ± 2 mV. 4 The onset of KvLQT1 channel inactivation during a single depolarization to +20 mV was exponential (τ= 130 ± 10 ms), and developed after a delay of ≈75 ms. In contrast, when inactivation was reinduced following transient recovery of channels to the open state(s), the onset of inactivation was immediate and 10 times faster. These findings suggest multiple open states, and a sequential gating model for KvLQT1 channel activation and inactivation (C 1 ⇌ C n ⇌ O 1 ⇌ O 2 ⇌ I). 5 Delayed rectifier K + ( I Ks ) channels formed by heteromultimeric coassembly of KvLQT1 and minimal K + channel (minK) subunits did not inactivate. Thus, minK subunits eliminate, or greatly slow, the gating associated with channel inactivation when coassembled with KvLQT1.