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Updated: Aug 9, 2026
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Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 1, 2010
Evolving potassium channels by means of yeast selection reveals structural elements important for selectivity
Delphine Bichet1, Yu-Fung Lin, Christian A Ibarra
1Departments of Physiology and Biochemistry, Howard Hughes Medical Institute, University of California, San Francisco, CA 94143-0725, USA.
Summary
Researchers identified key structural elements in potassium channels that restore selectivity for potassium ions over sodium ions. Mutations in transmembrane segments and pore helix regions were found to be crucial for this ion selectivity and channel function.
Area of Science:
- Biophysics
- Molecular Biology
- Ion Channel Physiology
Background:
- Potassium channels are vital for numerous physiological processes, including nerve signaling and heart rate regulation.
- Accurate ion selectivity, allowing potassium (K+) but not sodium (Na+) passage, is critical for channel function.
- The K+ channel signature sequence in the selectivity filter is necessary but not sufficient for K+ selectivity.
Purpose of the Study:
- To identify structural elements within the GIRK2 potassium channel that are essential for K+ selectivity.
- To investigate the relationship between ion permeation and channel gating mechanisms.
Main Methods:
- Random mutagenesis of the GIRK2 channel, specifically targeting the S177W mutation.
- Utilizing a yeast complementation assay to assess K+ transport deficiency and restoration.
- Single-channel analyses to evaluate channel gating properties.
Main Results:
- Mutations conferring constitutive activity (S177W) abolished K+ selectivity.
- Suppressor mutations in transmembrane segments and the pore helix partially restored K+ selectivity.
- Some suppressor mutations also influenced channel gating, affecting open time and frequency.
Conclusions:
- Structural elements beyond the canonical selectivity filter, including transmembrane segments and pore helix, play critical roles in K+ selectivity.
- An intricate interplay exists between ion permeation pathways and channel gating mechanisms in potassium channels.
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