Rapid and slow voltage-dependent conformational changes in segment IVS6 of voltage-gated Na+ channels

Vasanth Vedantham, Stephen C. Cannon

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Mutations in segment IVS6 of voltage-gated Na+ channels affect fast- inactivation, slow-inactivation, local anesthetic action, and batrachotoxin (BTX) action. To detect conformational changes associated with these processes, we substituted a cysteine for a valine at position 1583 in the rat adult skeletal muscle sodium channel α-subunit, and examined the accessibility of the substituted cysteine to modification by 2-aminoethyl methanethiosulfonate (MTS-EA) in excised macropatches. MTS-EA causes an irreversible reduction in the peak current when applied both internally and externally, with a reaction rate that is strongly voltage-dependent. The rate increased when exposures to MTS-EA occurred during brief conditioning pulses to progressively more depolarized voltages, but decreased when exposures occurred at the end of prolonged depolarizations, revealing two conformational changes near site 1583, one coupled to fast inactivation, and one tightly associated with slow inactivation. Tetraethylammonium, a pore blocker, did not affect the reaction rate from either direction, while BTX, a lipophilic activator of sodium channels, completely prevented the modification reaction from occurring from either direction. We conclude that there are two inactivation-associated conformational changes in the vicinity of site 1583, that the reactive site most likely faces away from the pore, and that site 1583 comprises part of the BTX receptor.

Original languageEnglish (US)
Pages (from-to)2943-2958
Number of pages16
JournalBiophysical Journal
Volume78
Issue number6
StatePublished - Jun 2000

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Batrachotoxins
Cysteine
Sodium Channel Agonists
Tetraethylammonium
Sodium Channels
Valine
Local Anesthetics
Catalytic Domain
Skeletal Muscle
Mutation
Direction compound

ASJC Scopus subject areas

  • Biophysics

Cite this

Rapid and slow voltage-dependent conformational changes in segment IVS6 of voltage-gated Na+ channels. / Vedantham, Vasanth; Cannon, Stephen C.

In: Biophysical Journal, Vol. 78, No. 6, 06.2000, p. 2943-2958.

Research output: Contribution to journalArticle

Vedantham, Vasanth ; Cannon, Stephen C. / Rapid and slow voltage-dependent conformational changes in segment IVS6 of voltage-gated Na+ channels. In: Biophysical Journal. 2000 ; Vol. 78, No. 6. pp. 2943-2958.
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