title: The P-region and S6 of Kv3.1 contribute to the formation of the ion conduction pathway.
abstract: The loop between transmembrane regions S5 and S6 (P-region) of voltage-gated K+ channels has been proposed to form the ion-conducting pore, and the internal part of this segment is reported to be responsible for ion permeation and internal tetraethylammonium (TEA) binding. The two T-cell K+ channels, Kv3.1 and Kv1.3, with widely divergent pore properties, differ by a single residue in this internal P-region, leucine 401 in Kv3.1 corresponding to valine 398 in Kv1.3. The L401V mutation in Kv3.1 was created with the anticipation that the mutant channel would exhibit Kv1.3-like deep-pore properties. Surprisingly, this mutation did not alter single channel conductance and only moderately enhanced internal TEA sensitivity, indicating that residues outside the P-region influence these properties. Our search for additional residues was guided by the model of Durell and Guy, which predicted that the C-terminal end of S6 formed part of the K+ conduction pathway. In this segment, the two channels diverge at only one position, Kv3.1 containing M430 in place of leucine in Kv1.3. The M430L mutant of Kv3.1 exhibited permeant ion- and voltage-dependent flickery outward single channel currents, with no obvious changes in other pore properties. Modification of one or more ion-binding sites located in the electric field and possibly within the channel pore could give rise to this type of channel flicker.
authors.affiliation: Department of Physiology and Biophysics, University of California, Irvine 92717.
authors.forename: J
authors.initials: J
authors.lastname: Aiyar
authors.forename: A N
authors.initials: AN
authors.lastname: Nguyen
authors.forename: K G
authors.initials: KG
authors.lastname: Chandy
authors.forename: S
authors.initials: S
authors.lastname: Grissmer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D055592:Biophysical Phenomena; D001703:Biophysics; D004563:Electrochemistry; D005260:Female; D066298:In Vitro Techniques; D017136:Ion Transport; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D009479:Neuropeptides; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014981:Xenopus
chemical_list: D009479:Neuropeptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium