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Effects of Kv1.2 Intracellular Regions on Activation of Kv2.1 Channels

Annette Scholle ^*, Thomas Zimmer ^*, Rolf Koopmann ^*, Birgit Engeland , Olaf Pongs  and Klaus Benndorf ^*

^* Institut für Physiologie II, Friedrich-Schiller-Universität, 07740 Jena, Germany; and Zentrum für Molekulare Neurobiologie, Institut für Neurale Signalverarbeitung, UKE Hamburg, 20251 Hamburg, Germany

Correspondence: Address reprint requests to Dr. Klaus Benndorf, Institut für Physiologie II, Friedrich-Schiller-Universität Jena, D-07740 Jena, Germany. Tel.: 49-3641-934351; Fax: 49-3641-933202; E-mail: klaus.Benndorf{at}mti.uni-jena.de.

Depolarizing voltage steps activate voltage-dependent K⁺ (Kv) channels by moving the voltage sensor, which triggers a coupling reaction leading to the opening of the pore. We constructed chimeric channels in which intracellular regions of slowly activating Kv2.1 channels were replaced by respective regions of rapidly activating Kv1.2 channels. Substitution of either the N-terminus, S4–S5 linker, or C-terminus generated chimeric Kv2.1/1.2 channels with a paradoxically slow and approximately exponential activation time course consisting of a fast and a slow component. Using combined chimeras, each of these Kv1.2 regions further slowed activation at the voltage of 0 mV, irrespective of the nature of the other two regions, whereas at the voltage of 40 mV both slowing and accelerating effects were observed. These results suggest voltage-dependent interactions of the three intracellular regions. This observation was quantified by double-mutant cycle analysis. It is concluded that interactions between N-terminus, S4–S5 linker, and/or C-terminus modulate the activation time course of Kv2.1 channels and that part of these interactions is voltage dependent.

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