The pore structure and gating mechanism of K2P channels

• DOI: 10.1038/emboj.2011.369
• Publication Date: 2011-11-02T14:43:19Z
• Authors: Paula L Piechotta; Markus Rapedius; Phillip J Stansfeld; Murali K Bollepalli; Gunter Ehrlich; Isabelle Andres-E...; Hariolf Fritzensc...; Niels Decher; Mark S P Sansom; Stephen J Tucker; Thomas Baukrowitz
• Keywords: 0303 health sciences; 03 medical and health sciences; Article

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.