Reconstituted voltage-sensitive sodium channel from Electrophorus electricus: chemical modifications that alter regulation of ion permeability.

E. C. Cooper, S. A. Tomiko, W. S. Agnew

Research output: Contribution to journalArticlepeer-review

Abstract

At equilibrium, voltage-sensitive sodium channels normally are closed at all potentials. They open transiently in response to changes in membrane voltage or chronically under the influence of certain neurotoxins. Covalent modifications that result in chronic opening may help identify molecular domains involved in conductance regulation. Here, the purified sodium channel from electric eel electroplax, reconstituted in artificial liposomes, has been used to screen for such modifications. When the liposomes were treated with the alkaloid neurotoxin batrachotoxin, sodium-selective ion fluxes were produced, with permeability ratios PNa greater than PTl greater than PK greater than PRb greater than PCs. When the liposomes were treated with either of two oxidizing reagents (N-bromoacetamide or N-bromosuccinimide), or with Pronase or trypsin, ion-selective fluxes also were stimulated. These were blocked by tetrodotoxin and the anesthetic QX-314 in a manner suggesting that only modification of the cytoplasmic protein surface resulted in stimulation. Limited exposure to trypsin resulted in strong flux activation, with the concomitant appearance of peptide fragments with masses of approximately equal to 130, 70, and 38 kDa and fragments with masses of 45 and 24 kDa appearing later. We propose that characterization of these fragments may allow identification of channel domains important for inactivation gating.

Original languageEnglish (US)
Pages (from-to)6282-6286
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume84
Issue number17
DOIs
StatePublished - Sep 1987

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'Reconstituted voltage-sensitive sodium channel from Electrophorus electricus: chemical modifications that alter regulation of ion permeability.'. Together they form a unique fingerprint.

Cite this