Dataset Information

Structural Basis for High-Affinity Trapping of the Na_V1.7 Channel in Its Resting State by Tarantula Toxin.

ABSTRACT: Voltage-gated sodium channels initiate electrical signals and are frequently targeted by deadly gating-modifier neurotoxins, including tarantula toxins, which trap the voltage sensor in its resting state. The structural basis for tarantula-toxin action remains elusive because of the difficulty of capturing the functionally relevant form of the toxin-channel complex. Here, we engineered the model sodium channel Na_VAb with voltage-shifting mutations and the toxin-binding site of human Na_V1.7, an attractive pain target. This mutant chimera enabled us to determine the cryoelectron microscopy (cryo-EM) structure of the channel functionally arrested by tarantula toxin. Our structure reveals a high-affinity resting-state-specific toxin-channel interaction between a key lysine residue that serves as a "stinger" and penetrates a triad of carboxyl groups in the S3-S4 linker of the voltage sensor. By unveiling this high-affinity binding mode, our studies establish a high-resolution channel-docking and resting-state locking mechanism for huwentoxin-IV and provide guidance for developing future resting-state-targeted analgesic drugs.

SUBMITTER: Wisedchaisri G

PROVIDER: S-EPMC8043720 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Publications

Structural Basis for High-Affinity Trapping of the Na<sub>V</sub>1.7 Channel in Its Resting State by Tarantula Toxin.

Wisedchaisri Goragot G Tonggu Lige L Gamal El-Din Tamer M TM McCord Eedann E Zheng Ning N Catterall William A WA

Molecular cell 20201123 1

Voltage-gated sodium channels initiate electrical signals and are frequently targeted by deadly gating-modifier neurotoxins, including tarantula toxins, which trap the voltage sensor in its resting state. The structural basis for tarantula-toxin action remains elusive because of the difficulty of capturing the functionally relevant form of the toxin-channel complex. Here, we engineered the model sodium channel Na<sub>V</sub>Ab with voltage-shifting mutations and the toxin-binding site of human N ...[more]

PMID: 33232657

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Project description:Allosteric ligands modulate protein activity by altering the energy landscape of conformational space in ligand-protein complexes. Here we investigate how ligand binding to a K+ channel's voltage sensor allosterically modulates opening of its K+-conductive pore. The tarantula venom peptide guangxitoxin-1E (GxTx) binds to the voltage sensors of the rat voltage-gated K+ (Kv) channel Kv2.1 and acts as a partial inverse agonist. When bound to GxTx, Kv2.1 activates more slowly, deactivates more rapidly, and requires more positive voltage to reach the same K+-conductance as the unbound channel. Further, activation kinetics are more sigmoidal, indicating that multiple conformational changes coupled to opening are modulated. Single-channel current amplitudes reveal that each channel opens to full conductance when GxTx is bound. Inhibition of Kv2.1 channels by GxTx results from decreased open probability due to increased occurrence of long-lived closed states; the time constant of the final pore opening step itself is not impacted by GxTx. When intracellular potential is less than 0 mV, GxTx traps the gating charges on Kv2.1's voltage sensors in their most intracellular position. Gating charges translocate at positive voltages, however, indicating that GxTx stabilizes the most intracellular conformation of the voltage sensors (their resting conformation). Kinetic modeling suggests a modulatory mechanism: GxTx reduces the probability of voltage sensors activating, giving the pore opening step less frequent opportunities to occur. This mechanism results in K+-conductance activation kinetics that are voltage-dependent, even if pore opening (the rate-limiting step) has no inherent voltage dependence. We conclude that GxTx stabilizes voltage sensors in a resting conformation, and inhibits K+ currents by limiting opportunities for the channel pore to open, but has little, if any, direct effect on the microscopic kinetics of pore opening. The impact of GxTx on channel gating suggests that Kv2.1's pore opening step does not involve movement of its voltage sensors.

Dataset Information

Structural Basis for High-Affinity Trapping of the Na_V1.7 Channel in Its Resting State by Tarantula Toxin.

Publications

Structural Basis for High-Affinity Trapping of the Na<sub>V</sub>1.7 Channel in Its Resting State by Tarantula Toxin.

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Dataset Information

Structural Basis for High-Affinity Trapping of the NaV1.7 Channel in Its Resting State by Tarantula Toxin.

Publications

Structural Basis for High-Affinity Trapping of the Na<sub>V</sub>1.7 Channel in Its Resting State by Tarantula Toxin.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Structural Basis for High-Affinity Trapping of the Na_V1.7 Channel in Its Resting State by Tarantula Toxin.