Hippocampal hypoglycaemia-activated K+ channels: single-channel analysis of glucose and voltage dependence

1994 ◽  
Vol 429 (1) ◽  
pp. 58-63 ◽  
Author(s):  
Cinzia Tromba ◽  
Antonino Salvaggio ◽  
Giorgio Racagni ◽  
Andrea Volterra
Keyword(s):  
Voltage Dependence ◽  
Single Channel ◽  
K Channels ◽  
Single Channel Analysis ◽  
Channel Analysis

scholarly journals Gating-dependent mechanism of 4-aminopyridine block in two related potassium channels.

1993 ◽  
Vol 102 (5) ◽  
pp. 797-816 ◽  
Author(s):  
G E Kirsch ◽  
J A Drewe
Keyword(s):  
Single Channel ◽  
K Channels ◽  
Voltage Gated ◽  
Gating Mechanism ◽  
Excitable Membranes ◽  
Single Channel Analysis ◽  
Channel Analysis ◽  
A Site ◽  
Selective Blocker ◽  
K Currents

4-aminopyridine (4AP) is widely used as a selective blocker of voltage-activated K+ currents in excitable membranes, but its mechanism and site of action at the molecular level are not well understood. To address this problem we have analyzed 4AP block in Kv2.1 and Kv3.1, mammalian representatives of the Drosophila Shab and Shaw subfamilies of voltage-gated K+ channels, respectively. The two channels were expressed in Xenopus oocytes and analyzed at both the macroscopic and single channel levels. Whole cell analysis showed that 4AP sensitivity of Kv3.1 was approximately 150 times greater than that of Kv2.1. Patch clamp analysis revealed that the mechanism of 4AP block in both channels was qualitatively similar. 4AP reached its blocking site via the cytoplasmic side of the channels, the ON rate for block was strongly accelerated when channels opened and the drug was trapped in closed channels. Single channel analysis showed that 4AP decreased burst duration and increased the latency-to-first-opening. These effects were found to be related, respectively to drug ON and OFF rates in the activated channel. Kv3.1's high 4AP sensitivity relative to Kv2.1 was associated with both a slower OFF rate and therefore increased stability of the blocked state, as well as a faster ON rate and therefore increased access to the binding site. Our results indicate that in both channels 4AP enters the intracellular mouth to bind to a site that is guarded by the gating mechanism. Differences in channel gating as well as differences in the structure of the intracellular mouth may be important for specifying the 4AP sensitivity in related voltage-gated K+ channels.

Single-channel analysis of a large conductance channel in peroxisomes from rat liver

1989 ◽  
Vol 984 (3) ◽  
pp. 351-359 ◽  
Author(s):  
Marc Lemmens ◽  
Kristine Verheyden ◽  
Paul Van Veldhoven ◽  
Johan Vereecke ◽  
Guy P. Mannaerts ◽  
...  
Keyword(s):  
Rat Liver ◽  
Single Channel ◽  
Single Channel Analysis ◽  
Large Conductance Channel ◽  
Channel Analysis
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