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Activation and deactivation properties of rat brain K+ channels of the Shakerrelated subfamily.
A Bertoli, O Moran, F Conti
Eur. Biophys. J.,
1994
, 23, 37984
We studied the activation properties of members of the Shakerrelated subfamily of voltagegated K+ channels cloned from rat brain and expressed in Xenopus oocytes. We find that Kv1.1, Kv1.4, Kv1.5, and Kv1.6 have similar activation and deactivation kinetics. The k+ currents produced by step depolarisations increase with a sigmoidal time course that can be described by a delay and by the derivative of the current at the inflection point. The delay tends to zero and the logarithmic derivative seems to approach a finite value at large positive voltages, but these asymptotic values are not yet reached at +80 mV. Deactivation of the currents upon stepping to negative membrane potentials below 60 mV is fairly well described by a single exponential. The decrease of the deactivation time constant at increasingly negative voltages tends to become less steep, indicating that this parameter also has a finite limiting value, which is not yet reached, however, at 160 mV. The various clones studied have very similar voltage dependencies of activation with halfactivation voltages ranging between 50 and 11 mV and maximum steepness yielding and efold change for voltage increments between 3.8 and 7.0 mV. The shallower activation curve of Kv1.4 is likely to be due to coupling with the fast inactivation process present in this clone.
http://www.ncbi.nlm.nih.gov/pubmed/7835322
