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Neuron. 1992 Mar;8(3):483-91.

The aromatic binding site for tetraethylammonium ion on potassium channels.

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1
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115.

Abstract

K+ channels are quite variable in their sensitivity to the pore-blocking agent tetraethylammonium ion (TEA) when it is applied to the extracellular side of the membrane. A Shaker K+ channel can be made highly sensitive by introducing a tyrosine (or phenylalanine) at residue 449 in each of the four subunits. A shift in the voltage dependence of blockade indicates that TEA senses a smaller fraction of the transmembrane electric field in the highly sensitive channels. There is a linear relationship between the free energy for TEA blockade and the number of subunits (zero, two, or four) containing tyrosine at 449, as if these four residues interact simultaneously with a TEA molecule to produce a high affinity binding site. The temperature dependence of blockade suggests that the interaction is not purely hydrophobic. These findings are consistent with a TEA-binding site formed by a bracelet of pore-lining aromatic residues. The center of the bracelet could bind a TEA molecule through a cation-pi orbital interaction.

PMID:
1550673
[Indexed for MEDLINE]
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