Molecular localization of an ion-binding site within the pore of mammalian sodium channels

Peter H. Backx, David T. Yue, John H. Lawrence, Eduardo Marban, Gordon F. Tomaselli

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Abstract

Sodium channels are the major proteins that underlie excitability in nerve, heart, and skeletal muscle. Chemical reaction rate theory was used to analyze the blockage of single wild-type and mutant sodium channels by cadmium ions. The affinity of cadmium for the native tetrodotoxin (TTX)-resistant cardiac channel was much higher than its affinity for the TTX-sensitive skeletal muscle isoform of the channel (μI). Mutation of Tyr401 to Cys, the corresponding residue in the cardiac sequence, rendered μI highly susceptible to cadmium blockage but resistant to TTX. The binding site was localized approximately 20% of the distance down the electrical field, thus defining the position of a critical residue within the sodium channel pore.

Original languageEnglish (US)
Pages (from-to)248-251
Number of pages4
JournalScience
Volume257
Issue number5067
DOIs
Publication statusPublished - Jan 1 1992
Externally publishedYes

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