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MinK residues line a potassium channel pore
K W Wang1, K K Tai, S A Goldstein
1Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Neuron
|March 1, 1996
Summary
MinK protein forms part of potassium (K+) channels, despite lacking typical pore-forming features. Specific mutations reveal a region involved in ion conduction, directly implicating MinK in forming K+ channel pores.
Area of Science:
- Molecular Biology
- Ion Channel Physiology
- Biophysics
Background:
- Potassium (K+) channels are crucial for cellular electrophysiology.
- MinK protein's role in K+ channel pore formation has been unclear due to its atypical structure.
- Known K+ channel subunits possess a P region and signature sequence, absent in MinK.
Purpose of the Study:
- To identify specific regions of MinK protein involved in K+ channel pore formation.
- To investigate the interaction of MinK with known K+ channel blockers.
- To elucidate the structural basis of MinK's contribution to ion conduction.
Main Methods:
- Site-directed mutagenesis of the MinK protein.
- Covalent and reversible blockade assays using methanethiosulfonate ethylsulfonate (MTSES) and tetraethylammonium (TEA).
- Analysis of voltage and ion concentration dependence of channel inhibition.
Main Results:
- A specific MinK region was identified that influences external blockade of K+ channel pores.
- Mutating residues in this region to cysteine conferred susceptibility to MTSES covalent blockade.
- These mutations also altered reversible inhibition by TEA, indicating overlapping binding sites for MTSES and TEA.
Conclusions:
- MinK protein directly participates in forming the K+-selective ion conduction pathway.
- The identified MinK region is critical for pore function and interaction with blockers.
- TEA blockade suggests MinK contributes to the external mouth of a transmembrane pore.