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Heteromultimerization between different potassium channel subunits can generate channels with novel functional properties and thus contributes to the rich functional diversity of this gene family. The inwardly rectifying potassium channel subunit Kir5.1 exhibits highly selective heteromultimerization with Kir4.1 to generate heteromeric Kir4.1/Kir5.1 channels with unique rectification and kinetic properties. These novel channels are also inhibited by intracellular pH within the physiological range and are thought to play a key role in linking K+ and H+ homeostasis by the kidney. However, the mechanisms that control heteromeric K+ channel assembly and the structural elements that generate their unique functional properties are poorly understood. In this study we identify residues at an intersubunit interface between the cytoplasmic domains of Kir5.1 and Kir4.1 that influence the novel rectification and gating properties of heteromeric Kir4.1/Kir5.1 channels and that also contribute to their pH sensitivity. Furthermore, this interaction presents a structural mechanism for the functional coupling of these properties and explains how specific heteromeric interactions can contribute to the novel functional properties observed in heteromeric Kir channels. The highly conserved nature of this structural association between Kir subunits also has implications for understanding the general mechanisms of Kir channel gating and their regulation by intracellular pH.

Original publication

DOI

10.1074/jbc.M306596200

Type

Journal article

Journal

J Biol Chem

Publication Date

31/10/2003

Volume

278

Pages

43533 - 43540

Keywords

Amino Acid Sequence, Animals, Cloning, Molecular, Cytoplasm, Electrophysiology, Hydrogen, Hydrogen-Ion Concentration, Models, Molecular, Molecular Sequence Data, Mutation, Potassium, Potassium Channels, Inwardly Rectifying, Protein Binding, Protein Structure, Tertiary, Sequence Homology, Amino Acid, Time Factors, Xenopus laevis