Yamane T, Furukawa T, Horikawa S, Hiraoka M
Department of Cardiovascular Diseases, Tokyo Medical and Dental University, Japan.
FEBS Lett. 1993 Mar 22;319(3):229-32. doi: 10.1016/0014-5793(93)80552-6.
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.
