External pH regulates the slowly activating potassium current IsK expressed in Xenopus oocytes.
A slowly activating, delayed rectifier potassium current, IsK, was expressed in Xenopus laevis oocytes by injection of cRNA transcribed from a rat kidney cDNA clone. External acidification reversibly decreased the current amplitude. The effects were concentration dependent on protons with Kd at pH approximately 5.5 and a Hill coefficient of 1.0. External acidification reduced the maximal conductance (Gmax) without affecting the activation kinetics; this effect was not dependent on membrane voltages. These data suggest that H+ ions bind to the channel with a one-to-one stoichiometry, and this binding site may be located outside of the membrane electric field.
Yamane
T
T
Department of Cardiovascular Diseases, Tokyo Medical and Dental University, Japan.
Furukawa
T
T
Horikawa
S
S
Hiraoka
M
M
D000818:Animals; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology; D009865:Oocytes; D011188:Potassium / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D011994:Recombinant Proteins; D014982:Xenopus laevis
D008565:Membrane Proteins; D015221:Potassium Channels; D011994:Recombinant Proteins; D011188:Potassium