title: A conserved glutamate is important for slow inactivation in K+ channels.
abstract: Voltage-gated ion channels undergo slow inactivation during prolonged depolarizations. We investigated the role of a conserved glutamate at the extracellular end of segment 5 (S5) in slow inactivation by mutating it to a cysteine (E418C in Shaker). We could lock the channel in two different conformations by disulfide-linking 418C to two different cysteines, introduced in the Pore-S6 (P-S6) loop. Our results suggest that E418 is normally stabilizing the open conformation of the slow inactivation gate by forming hydrogen bonds with the P-S6 loop. Breaking these bonds allows the P-S6 loop to rotate, which closes the slow inactivation gate. Our results also suggest a mechanism of how the movement of the voltage sensor can induce slow inactivation by destabilizing these bonds.
authors.affiliation: Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden. peter.larsson@neuro.ki.se
authors.forename: H P
authors.initials: HP
authors.lastname: Larsson
authors.forename: F
authors.initials: F
authors.lastname: Elinder
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D019943:Amino Acid Substitution; D000818:Animals; D001464:Barium / Q000494:pharmacology; D017124:Conserved Sequence / Q000235:genetics*; D004220:Disulfides / Q000737:chemistry; D018698:Glutamic Acid / Q000235:genetics*; D006860:Hydrogen Bonding; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010618:Phenanthrolines / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D019163:Reducing Agents / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014162:Transfection; D014981:Xenopus
chemical_list: D004220:Disulfides; D010618:Phenanthrolines; D015221:Potassium Channels; D019163:Reducing Agents; D001464:Barium; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; C025205:1,10-phenanthroline