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Molecular basis of ion permeability in a voltage‐gated sodium channel
Author(s) -
Naylor Claire E,
Bagnéris Claire,
DeCaen Paul G,
Sula Altin,
Scaglione Antonella,
Clapham David E,
Wallace BA
Publication year - 2016
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.15252/embj.201593285
Subject(s) - sodium , ion , potassium , sodium channel , selectivity , ion channel , kcsa potassium channel , biophysics , potassium channel , permeability (electromagnetism) , membrane , extracellular , chemistry , inorganic chemistry , materials science , biology , biochemistry , organic chemistry , catalysis , receptor
Voltage‐gated sodium channels are essential for electrical signalling across cell membranes. They exhibit strong selectivities for sodium ions over other cations, enabling the finely tuned cascade of events associated with action potentials. This paper describes the ion permeability characteristics and the crystal structure of a prokaryotic sodium channel, showing for the first time the detailed locations of sodium ions in the selectivity filter of a sodium channel. Electrostatic calculations based on the structure are consistent with the relative cation permeability ratios (Na + ≈ Li + ≫ K + , Ca 2+ , Mg 2+ ) measured for these channels. In an E178D selectivity filter mutant constructed to have altered ion selectivities, the sodium ion binding site nearest the extracellular side is missing. Unlike potassium ions in potassium channels, the sodium ions in these channels appear to be hydrated and are associated with side chains of the selectivity filter residues, rather than polypeptide backbones.