Structure and function of the voltage sensor of sodium channels probed by a β-scorpion toxin

Sandrine Cestèle, Vladimir Yarov-Yarovoy, Yusheng Qu, François Sampieri, Todd Scheuer, William A. Catterall

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

Voltage sensing by voltage-gated sodium channels determines the electrical excitability of cells, but the molecular mechanism is unknown. β-Scorpion toxins bind specifically to neurotoxin receptor site 4 and induce a negative shift in the voltage dependence of activation through a voltage sensor-trapping mechanism. Kinetic analysis showed that β-scorpion toxin binds to the resting state, and subsequently the bound toxin traps the voltage sensor in the activated state in a voltage-dependent but concentration-independent manner. The rate of voltage sensor trapping can be fit by a two-step model, in which the first step is voltage-dependent and correlates with the outward gating movement of the IIS4 segment, whereas the second step is voltage-independent and results in shifted voltage dependence of activation of the channel. Mutations of Glu779 in extracellular loop IIS1-S2 and both Glu837 and Leu840 in extracellular loop IIS3-S4 reduce the binding affinity of β-scorpion toxin. Mutations of positively charged and hydrophobic amino acid residues in the IIS4 segment do not affect β-scorpion toxin binding but alter voltage dependence of activation and enhance β-scorpion toxin action. Structural modeling with the Rosetta algorithm yielded a three-dimensional model of the toxin-receptor complex with the IIS4 voltage sensor at the extracellular surface. Our results provide mechanistic and structural insight into the voltage sensor-trapping mode of scorpion toxin action, define the position of the voltage sensor in the resting state of the sodium channel, and favor voltage-sensing models in which the S4 segment spans the membrane in both resting and activated states.

Original languageEnglish (US)
Pages (from-to)21332-21344
Number of pages13
JournalJournal of Biological Chemistry
Volume281
Issue number30
DOIs
StatePublished - Jul 28 2006
Externally publishedYes

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Scorpions
Sodium Channels
Sensors
Electric potential
Voltage-Gated Sodium Channels
Mutation
Neurotoxins
Chemical activation
Amino Acids
Membranes

ASJC Scopus subject areas

  • Biochemistry

Cite this

Structure and function of the voltage sensor of sodium channels probed by a β-scorpion toxin. / Cestèle, Sandrine; Yarov-Yarovoy, Vladimir; Qu, Yusheng; Sampieri, François; Scheuer, Todd; Catterall, William A.

In: Journal of Biological Chemistry, Vol. 281, No. 30, 28.07.2006, p. 21332-21344.

Research output: Contribution to journalArticle

Cestèle, Sandrine ; Yarov-Yarovoy, Vladimir ; Qu, Yusheng ; Sampieri, François ; Scheuer, Todd ; Catterall, William A. / Structure and function of the voltage sensor of sodium channels probed by a β-scorpion toxin. In: Journal of Biological Chemistry. 2006 ; Vol. 281, No. 30. pp. 21332-21344.
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