Enhanced closed-state inactivation in a mutant Shaker K+ channel

Many mutations that shift the voltage dependence of activation in Shaker channels cause a parallel shift of inactivation. The I2 mutation (L382I in the Shaker B sequence) is an exception, causing a 45 mV activation shift with only a 9 mV shift of inactivation midpoint relative to the wildtype (WT) c...

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Bibliographic Details
Published in:The Journal of membrane biology 1997-06, Vol.157 (3), p.215-230
Main Authors: Ayer, Jr, R K, Sigworth, F J
Format: Article
Language:English
Subjects:
Animals
Drosophila
Drosophila Proteins
Ion Channel Gating - genetics
Mutation
Patch-Clamp Techniques
Potassium Channels - genetics
Potassium Channels - metabolism
Shaker Superfamily of Potassium Channels
Xenopus
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Summary:Many mutations that shift the voltage dependence of activation in Shaker channels cause a parallel shift of inactivation. The I2 mutation (L382I in the Shaker B sequence) is an exception, causing a 45 mV activation shift with only a 9 mV shift of inactivation midpoint relative to the wildtype (WT) channel. We compare the behavior of WT and I2 Shaker 29-4 channels in macropatch recordings from Xenopus oocytes. The behavior of WT channels can be described by both simple and detailed kinetic models which assume that inactivation proceeds only from the open state. The behavior of I2 channels requires that they inactivate from closed states as well, a property characteristic of voltage-gated sodium channels. A detailed "multiple-state inactivation" model is presented that describes both activation and inactivation of I2 channels. The results are consistent with the view that residue L382 is associated with the receptor for the inactivation particles in Shaker channels.
ISSN:0022-2631
1432-1424
DOI:10.1007/s002329900230