Murine Kcnk3 channels function as potassium-selective leak conductances that open across physiological voltages but are inhibited by physiological proton levels in a potassium-sensitive manner.
The study characterizes the biophysical properties of the murine cardiac leak channel Kcnk3, demonstrating that its proton block and voltage gating are potassium-dependent.
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.
Lopes et al. (Thu,) conducted a other in Murine cardiac leak channel Kcnk3. Murine Kcnk3 channels function as potassium-selective leak conductances that open across physiological voltages but are inhibited by physiological proton levels in a potassium-sensitive manner.