Anomalous mole fraction effect induced by mutation of the H5 pore region in the Shaker K+ channel

Mutagenesis of the H5 region of the Shaker K+ channel has provided strong evidence that these amino acids form a major portion of the ionic pore. We have previously observed that a single-site mutation (T441S) in this region increased the apparent relative permeability of the channel to NH4+. We now...

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Bibliographic Details
Published in:Biophysical journal 1996-11, Vol.71 (5), p.2467-2472
Main Authors: Yool, A.J., Schwarz, T.L.
Format: Article
Language:English
Subjects:
Animals
Electric Conductivity
Ion Channel Gating
Membrane Potentials
Mutagenesis, Site-Directed
Oocytes
Patch-Clamp Techniques
Point Mutation
Potassium - physiology
Potassium Channels - chemistry
Potassium Channels - physiology
Quaternary Ammonium Compounds - metabolism
Recombinant Fusion Proteins
Structure-Activity Relationship
Xenopus laevis
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Summary:Mutagenesis of the H5 region of the Shaker K+ channel has provided strong evidence that these amino acids form a major portion of the ionic pore. We have previously observed that a single-site mutation (T441S) in this region increased the apparent relative permeability of the channel to NH4+. We now report that this increased relative permeability to NH4+ is sensitive to small changes in external K+ in a pattern consistent with an anomalous mole fraction effect. The effect is not apparent in the wild-type channel. These findings, in combination with other studies showing effects of this particular mutation on the binding of tetraethylammonium and hydroxylamine, support the hypothesis that T441S alters the affinity of a putative ion binding site for NH4+ and ammonium derivatives. The mutation T441S alters ionic selectivity and reveals the multi-ion nature of the mutant Shaker K+ channel.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(96)79440-7