Structural basis for gating charge movement in the voltage sensor of a sodium channel

TitleStructural basis for gating charge movement in the voltage sensor of a sodium channel
Publication TypeJournal Article
Year of Publication2012
AuthorsYarov-Yarovoy, V., DeCaen P. G., Westenbroek R. E., Pan C. - Y., Scheuer T., Baker D., & Catterall W. A.
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue2
PaginationE93-102
Date Published2012 Jan 10
ISSN1091-6490
KeywordsCollaborative Publication
Abstract

Voltage-dependent gating of ion channels is essential for electrical signaling in excitable cells, but the structural basis for voltage sensor function is unknown. We constructed high-resolution structural models of resting, intermediate, and activated states of the voltage-sensing domain of the bacterial sodium channel NaChBac using the Rosetta modeling method, crystal structures of related channels, and experimental data showing state-dependent interactions between the gating charge-carrying arginines in the S4 segment and negatively charged residues in neighboring transmembrane segments. The resulting structural models illustrate a network of ionic and hydrogen-bonding interactions that are made sequentially by the gating charges as they move out under the influence of the electric field. The S4 segment slides 6-8 Å outward through a narrow groove formed by the S1, S2, and S3 segments, rotates ∼30°, and tilts sideways at a pivot point formed by a highly conserved hydrophobic region near the middle of the voltage sensor. The S4 segment has a 3(10)-helical conformation in the narrow inner gating pore, which allows linear movement of the gating charges across the inner one-half of the membrane. Conformational changes of the intracellular one-half of S4 during activation are rigidly coupled to lateral movement of the S4-S5 linker, which could induce movement of the S5 and S6 segments and open the intracellular gate of the pore. We confirmed the validity of these structural models by comparing with a high-resolution structure of a NaChBac homolog and showing predicted molecular interactions of hydrophobic residues in the S4 segment in disulfide-locking studies.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
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