EMD-25919
Cryo-EM structure of the human Nax channel in complex with beta3 solved in nanodiscs
EMD-25919
Single-particle3.2 Å
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Map released: 30/03/2022
Last modified: 06/11/2024
Sample Organism:
Homo sapiens
Sample: Complex of human Nax with the Beta3 auxiliary subunit
Fitted models: 7tj8 (Avg. Q-score: 0.512)
Deposition Authors: Noland CL, Kschonsak M, Ciferri C
,
Payandeh J
Sample: Complex of human Nax with the Beta3 auxiliary subunit
Fitted models: 7tj8 (Avg. Q-score: 0.512)
Deposition Authors: Noland CL, Kschonsak M, Ciferri C
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Structure-guided unlocking of Na X reveals a non-selective tetrodotoxin-sensitive cation channel.
Noland CL,
Chua HC
,
Kschonsak M,
Heusser SA
,
Braun N
,
Chang T,
Tam C,
Tang J,
Arthur CP,
Ciferri C
,
Pless SA
,
Payandeh J
(2022) Nat Commun , 13 , 1416 - 1416
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(2022) Nat Commun , 13 , 1416 - 1416
Abstract:
Unlike classical voltage-gated sodium (NaV) channels, NaX has been characterized as a voltage-insensitive, tetrodotoxin-resistant, sodium (Na+)-activated channel involved in regulating Na+ homeostasis. However, NaX remains refractory to functional characterization in traditional heterologous systems. Here, to gain insight into its atypical physiology, we determine structures of the human NaX channel in complex with the auxiliary β3-subunit. NaX reveals structural alterations within the selectivity filter, voltage sensor-like domains, and pore module. We do not identify an extracellular Na+-sensor or any evidence for a Na+-based activation mechanism in NaX. Instead, the S6-gate remains closed, membrane lipids fill the central cavity, and the domain III-IV linker restricts S6-dilation. We use protein engineering to identify three pore-wetting mutations targeting the hydrophobic S6-gate that unlock a robust voltage-insensitive leak conductance. This constitutively active NaX-QTT channel construct is non-selective among monovalent cations, inhibited by extracellular calcium, and sensitive to classical NaV channel blockers, including tetrodotoxin. Our findings highlight a functional diversity across the NaV channel scaffold, reshape our understanding of NaX physiology, and provide a template to demystify recalcitrant ion channels.
Unlike classical voltage-gated sodium (NaV) channels, NaX has been characterized as a voltage-insensitive, tetrodotoxin-resistant, sodium (Na+)-activated channel involved in regulating Na+ homeostasis. However, NaX remains refractory to functional characterization in traditional heterologous systems. Here, to gain insight into its atypical physiology, we determine structures of the human NaX channel in complex with the auxiliary β3-subunit. NaX reveals structural alterations within the selectivity filter, voltage sensor-like domains, and pore module. We do not identify an extracellular Na+-sensor or any evidence for a Na+-based activation mechanism in NaX. Instead, the S6-gate remains closed, membrane lipids fill the central cavity, and the domain III-IV linker restricts S6-dilation. We use protein engineering to identify three pore-wetting mutations targeting the hydrophobic S6-gate that unlock a robust voltage-insensitive leak conductance. This constitutively active NaX-QTT channel construct is non-selective among monovalent cations, inhibited by extracellular calcium, and sensitive to classical NaV channel blockers, including tetrodotoxin. Our findings highlight a functional diversity across the NaV channel scaffold, reshape our understanding of NaX physiology, and provide a template to demystify recalcitrant ion channels.