title: The pore structure and gating mechanism of K2P channels.
abstract: Two-pore domain (K2P) potassium channels are important regulators of cellular electrical excitability. However, the structure of these channels and their gating mechanism, in particular the role of the bundle-crossing gate, are not well understood. Here, we report that quaternary ammonium (QA) ions bind with high-affinity deep within the pore of TREK-1 and have free access to their binding site before channel activation by intracellular pH or pressure. This demonstrates that, unlike most other K(+) channels, the bundle-crossing gate in this K2P channel is constitutively open. Furthermore, we used QA ions to probe the pore structure of TREK-1 by systematic scanning mutagenesis and comparison of these results with different possible structural models. This revealed that the TREK-1 pore most closely resembles the open-state structure of KvAP. We also found that mutations close to the selectivity filter and the nature of the permeant ion profoundly influence TREK-1 channel gating. These results demonstrate that the primary activation mechanisms in TREK-1 reside close to, or within the selectivity filter and do not involve gating at the cytoplasmic bundle crossing.
authors.affiliation: Universitätsklinikum Jena, Institute of Physiology II, Jena, Germany.
authors.forename: Paula L
authors.initials: PL
authors.lastname: Piechotta
authors.forename: Markus
authors.initials: M
authors.lastname: Rapedius
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Stansfeld
authors.forename: Murali K
authors.initials: MK
authors.lastname: Bollepalli
authors.forename: Gunter
authors.initials: G
authors.lastname: Ehrlich
authors.forename: Gunter
authors.initials: G
authors.lastname: Erhlich
authors.forename: Isabelle
authors.initials: I
authors.lastname: Andres-Enguix
authors.forename: Hariolf
authors.initials: H
authors.lastname: Fritzenschaft
authors.forename: Niels
authors.initials: N
authors.lastname: Decher
authors.forename: Mark S P
authors.initials: MS
authors.lastname: Sansom
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Tucker
authors.forename: Thomas
authors.initials: T
authors.lastname: Baukrowitz
mesh_terms: D000818:Animals; D001665:Binding Sites; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D009154:Mutation; D016062:Porosity; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D051381:Rats
chemical_list: D026902:Potassium Channel Blockers; D024683:Potassium Channels, Tandem Pore Domain; D000644:Quaternary Ammonium Compounds; C103742:potassium channel protein TREK-1