Crystal Structure of a Voltage-gated K+ Channel Pore Module in a Closed State in Lipid Membranes

Jose S Santos,Guillermo A Asmar-Rovira,Gye Won Han,Wei Liu,Ruhma Syeda,Vadim Cherezov,Kent A Baker,Raymond C Stevens,Mauricio Montal

doi:10.1074/jbc.m112.415091

Jose S Santos, Guillermo A Asmar-Rovira + Show 7 more

Open Access

https://doi.org/10.1074/jbc.m112.415091

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Abstract

Voltage-gated K(+) channels underlie the electrical excitability of cells. Each subunit of the functional tetramer consists of the tandem fusion of two modules, an N-terminal voltage-sensor and a C-terminal pore. To investigate how sensor coupling to the pore generates voltage-dependent channel opening, we solved the crystal structure and characterized the function of a voltage-gated K(+) channel pore in a lipid membrane. The structure of a functional channel in a membrane environment at 3.1 Å resolution establishes an unprecedented connection between channel structure and function. The structure is unique in delineating an ion-occupied ready to conduct selectivity filter, a confined aqueous cavity, and a closed activation gate, embodying a dynamic entity trapped in an unstable closed state.

Highlights

Structures of functional Kϩ channels in lipid membranes are lacking
A crystal structure solved at 3.1 Å (Fig. 1, B and C) in a monoolein (1-oleoyl-rac-glycerol) membrane shows that the KvLm PM shares the funnel architecture of other Kϩ channels (5, 6, 20, 26 –28)
Each subunit contributes two transmembrane helices (outer helix or transmembrane segments (TMs) S5 (Gly15–Ile7) inner helix or TM S6 (Pro-68 to Thr-93) tilted with respect to the lipid bilayer normal, a pore helix (Tyr44–Ala55) with the C-end directed to the pore lumen, and the selectivity filter (Thr56– Asp62) formed at the center of the tetrameric channel (Figs. 1, A and B, and 2A)

Summary

Background

Structures of functional Kϩ channels in lipid membranes are lacking. Results: We dissected the pore module from the intact subunit, demonstrated its functional competence, and determined its crystal structure in membranes. Voltage-gated K؉ channels underlie the electrical excitability of cells. Each subunit of the functional tetramer consists of the tandem fusion of two modules, an N-terminal voltage-sensor and a C-terminal pore. To investigate how sensor coupling to the pore generates voltage-dependent channel opening, we solved the crystal structure and characterized the function of a voltage-gated K؉ channel pore in a lipid membrane. Voltage-gated Kϩ channels (Kv) are pivotal underpins of electrically excitable cells [1]. Each subunit consists of two tandemly arranged structural modules: an N-terminal voltage sensor module encompassing four transmembrane segments (TMs) S1–S4 and a C-terminal pore (PM) consisting of TMs S5 and S6 [2,3,4,5,6]. We present the structure of such PM obtained from diffraction quality crystals using the lipidic cubic phase approach [8, 9]

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION