Proton block and voltage gating are potassium-dependent in the cardiac leak channel Kcnk3.
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
C M
CM
Section of Developmental Biology and Biophysics, Departments of Pediatrics and Cellular and Molecular Physiology, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06536, USA.
Gallagher
P G
PG
Buck
M E
ME
Butler
M H
MH
Goldstein
S A
SA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism* / Q000502:physiology; D024683:Potassium Channels, Tandem Pore Domain; D011522:Protons; D014982:Xenopus laevis
D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D011522:Protons; C420132:potassium channel subfamily K member 3; D011188:Potassium