title: Role of the S2 and S3 segment in determining the activation kinetics in Kv2.1 channels.
abstract: We constructed chimeras between the rapidly activating Kv1.2 channel and the slowly activating Kv2.1 channel in order to study to what extent sequence differences within the S1-S4 region contribute to the difference in activation kinetics. The channels were expressed in Xenopus oocytes and the currents were measured with a two-microelectrode voltage-clamp technique. Substitution of the S1-S4 region of Kv2.1 subunits by the ones of Kv1.2 resulted in chimeric channels which activated more rapidly than Kv2.1. Furthermore, activation kinetics were nearly voltage-independent in contrast to the pronounced voltage-dependent activation kinetics of both parent channels. Systematic screening of the S1-S4 region by the replacement of smaller protein parts resolved that the main functional changes generated by the S1-S4 substitution were generated by the S2 and the S3 segment. However, the effects of these segments were different: The S3 substitution reduced the effective gating charge and accelerated both a voltage-dependent and a voltage-independent component of the activation time course. In contrast, the S2 substitution accelerated predominantly the voltage-dependent component of the activation time course thereby leaving the effective gating charge unchanged. It is concluded that the S2 and the S3 segment determine the activation kinetics in a specific manner.
authors: Institut für Physiologie, Herz-Kreislauf-Physiologie, Friedrich-Schiller-Universität, 07740 Jena, Germany.
authors: R
authors: R
authors: Koopmann
authors: A
authors: A
authors: Scholle
authors: J
authors: J
authors: Ludwig
authors: T
authors: T
authors: Leicher
authors: T
authors: T
authors: Zimmer
authors: O
authors: O
authors: Pongs
authors: K
authors: K
authors: Benndorf
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D051668:Delayed Rectifier Potassium Channels; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D007700:Kinetics; D051663:Kv1.2 Potassium Channel; D008845:Microinjections; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000737:chemistry*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D051669:Shab Potassium Channels; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
chemical_list: D051668:Delayed Rectifier Potassium Channels; C496969:KCNA2 protein, human; C496988:KCNB1 protein, human; C496972:Kcna2 protein, rat; C496991:Kcnb1 protein, rat; D051663:Kv1.2 Potassium Channel; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D051669:Shab Potassium Channels