Localization and molecular determinants of the Hanatoxin receptors on the voltage-sensing domains of a K(+) channel.
Hanatoxin inhibits voltage-gated K(+) channels by modifying the energetics of activation. We studied the molecular determinants and physical location of the Hanatoxin receptors on the drk1 voltage-gated K(+) channel. First, we made multiple substitutions at three previously identified positions in the COOH terminus of S3 to examine whether these residues interact intimately with the toxin. We also examined a region encompassing S1-S3 using alanine-scanning mutagenesis to identify additional determinants of the toxin receptors. Finally, guided by the structure of the KcsA K(+) channel, we explored whether the toxin interacts with the peripheral extracellular surface of the pore domain in the drk1 K(+) channel. Our results argue for an intimate interaction between the toxin and the COOH terminus of S3 and suggest that the Hanatoxin receptors are confined within the voltage-sensing domains of the channel, at least 20-25 A away from the central pore axis.
Li-Smerin
Y
Y
Molecular Physiology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Swartz
K J
KJ
D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D051668:Delayed Rectifier Potassium Channels; D004558:Electric Stimulation; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics*; D024642:Potassium Channels, Voltage-Gated; D020836:Protein Structure, Quaternary; D014982:Xenopus laevis
D051668:Delayed Rectifier Potassium Channels; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C096469:hanatoxin; D000409:Alanine