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MinK potassium channels are heteromultimeric complexes
K K Tai1, K W Wang, S A Goldstein
1Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536-0812, USA.
The Journal of Biological Chemistry
|January 17, 1997
Summary
The potassium channel MinK (Mink) requires an associated oocyte protein for proper function. Modifying this protein changes the ion pore, affecting potassium, sodium, and cesium flow.
Area of Science:
- Molecular biology
- Ion channel physiology
- Biochemistry
Background:
- MinK is a transmembrane protein crucial for potassium currents in mammals.
- Its function in Xenopus laevis oocytes suggests interaction with endogenous proteins.
- Previous studies hinted at, but did not confirm, MinK's association with other proteins.
Purpose of the Study:
- To investigate the role of associated proteins in MinK ion channel function.
- To determine if MinK directly interacts with oocyte membrane proteins.
- To characterize the functional consequences of modifying such associated proteins.
Main Methods:
- Expression of MinK in Xenopus laevis oocytes.
- Covalent modification of oocyte membrane proteins using sulfhydryl-specific methanethiosulfonate derivatives.
- Electrophysiological analysis of ion currents (potassium, sodium, cesium) through modified channels.
Main Results:
- Direct covalent modification of an oocyte membrane protein altered MinK channel properties.
- Modified channels showed reduced potassium conduction.
- Increased permeability to sodium and cesium ions was observed in modified channels.
- Modification rates depended on the channel's conformational state, indicating extracellular accessibility.
Conclusions:
- MinK intimately associates with an endogenous oocyte protein.
- This associated protein's extracellular exposure varies with channel gating.
- The oocyte protein is essential for establishing the ion conduction pore function of MinK.