Neuron
Volume 7, Issue 3, September 1991, Pages 403-408
Journal home page for Neuron

Article
Site-specific mutations in a minimal voltage-dependent K+ channel alter ion selectivity and open-channel block

https://doi.org/10.1016/0896-6273(91)90292-8Get rights and content

Abstract

MinK is a small membrane protein of 130 amino acids with a single potential membrane-spanning a-helical domain. Its expression in Xenopus oocytes induces voltage-dependent, K+-selective channels. Using site-directed mutagenesis of a synthetic gene, we have identified residues in the hydrophobic region of minK that influence both ion selectivity and open-channel block. Single amino acid changes increase the channel's relative permeability for NH4+ and Cs+ without affecting its ability to exclude Na+and Li+. Blockade by two common K+ channel pore blockers, tetraethylammonium and Cs+, was also modified. These results suggest that an ion selectivity region and binding sites for the pore blockers within the conduction pathway have been modified. We conclude that the gene encoding minK is a structural gene for a K+ channel protein.

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