Mechanisms of maurotoxin action on Shaker potassium channels.
Maurotoxin (alpha-KTx6.2) is a toxin derived from the Tunisian chactoid scorpion Scorpio maurus palmatus, and it is a member of a new family of toxins that contain four disulfide bridges (, Eur. J. Biochem. 254:468-479). We investigated the mechanism of the maurotoxin action on voltage-gated K(+) channels expressed in Xenopus oocytes. Maurotoxin blocks the channels in a voltage-dependent manner, with its efficacy increasing with greater hyperpolarization. We show that an amino acid residue in the external mouth of the channel pore segment that is known to be involved in the actions of other peptide toxins is also involved in maurotoxin's interaction with the channel. We conclude that, despite the unusual disulfide bridge pattern, the mechanism of the maurotoxin action is similar to those of other K(+) channel toxins with only three disulfide bridges.
Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242, USA.
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Avdonin
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Nolan
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Sabatier
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De Waard
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Hoshi
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D018999:Charybdotoxin / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects; D008390:Markov Chains; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009498:Neurotoxins / Q000494:pharmacology; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry; D012604:Scorpion Venoms / Q000737:chemistry / Q000494:pharmacology*; D016415:Sequence Alignment; D017384:Sequence Deletion; D051637:Shaker Superfamily of Potassium Channels; D014982:Xenopus laevis
D009498:Neurotoxins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011994:Recombinant Proteins; D012604:Scorpion Venoms; D051637:Shaker Superfamily of Potassium Channels; C104498:maurotoxin; D018999:Charybdotoxin