Proton block and voltage gating are potassium-dependent in the cardiac leak channel Kcnk3.
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Lopes CM, Gallagher PG, Buck ME, Butler MH, Goldstein SA
Proton block and voltage gating are potassium-dependent in the cardiac leak channel Kcnk3.
J Biol Chem. 2000 Jun 2;275(22):16969-78.
- PubMed ID
- 10748056 [ View in PubMed]
- Abstract
Potassium leak conductances were recently revealed to exist as independent molecular entities. Here, the genomic structure, cardiac localization, and biophysical properties of a murine example are considered. Kcnk3 subunits have two pore-forming P domains and unique functional attributes. At steady state, Kcnk3 channels behave like open, potassium-selective, transmembrane holes that are inhibited by physiological levels of proton. With voltage steps, Kcnk3 channels open and close in two phases, one appears to be immediate and one is time-dependent (tau = approximately 5 ms). Both proton block and gating are potassium-sensitive; this produces an anomalous increase in outward flux as external potassium levels rise because of decreased proton block. Single Kcnk3 channels open across the physiological voltage range; hence they are "leak" conductances; however, they open only briefly and rarely even after exposure to agents that activate other potassium channels.