Mutations in the K+ channel signature sequence.
Potassium channels share a highly conserved stretch of eight amino acids, a K+ channel signature sequence. The conserved sequence falls within the previously defined P-region of voltage-activated K+ channels. In this study we investigate the effect of mutations in the signature sequence of the Shaker channel on K+ selectivity determined under bi-ionic conditions. Nonconservative substitutions of two threonine residues and the tyrosine residue leave selectivity intact. In contrast, mutations at some positions render the channel nonselective among monovalent cations. These findings are consistent with a proposal that the signature sequence contributes to a selectivity filter. Furthermore, the results illustrate that the hydroxyl groups at the third and fourth positions, and the aromatic group at position seven, are not essential in determining K+ selectivity.
Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115.
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Heginbotham
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Abramson
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MacKinnon
D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D017124:Conserved Sequence; D004330:Drosophila / Q000235:genetics; D005260:Female; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010641:Phenotype; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D015221:Potassium Channels; D011188:Potassium