Block of ShakerB K+ channels by Pi1, a novel class of scorpion toxin.
Here we describe the basic features of the interaction of K+ channels with Pi1, a recently described 35 amino acid scorpion toxin, which has four disulfide bridges instead of the three commonly found in all the other known scorpion toxins. We found that: (a) Pi1 blocks ShakerB from the outside with a 1:1 stoichiometry, and a Kd of 32 nM in zero external [K+]; (b) extracellular K+, Rb+ and Cs+ but not NH4+ ions strongly impede (destabilize) the block by this toxin; interestingly (c) the destabilizing binding of K+, Rb+, and Cs+ is described by a Hill coefficient n > 1; (d) external K+ is more effective than internal K+ to reduce the block by Pi1.
Gómez-Lagunas
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F
Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, Universidad Nacional Autónoma de México, Cuernavaca.
Olamendi-Portugal
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Possani
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LD
D000818:Animals; D002412:Cations; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000037:antagonists & inhibitors* / Q000235:genetics; D012604:Scorpion Venoms / Q000494:pharmacology*; D012605:Scorpions / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels; D012964:Sodium / Q000378:metabolism; D018411:Spodoptera / Q000166:cytology
D002412:Cations; D010455:Peptides; D012604:Scorpion Venoms; C076413:Shaker B potassium channel polypeptide; D051637:Shaker Superfamily of Potassium Channels; D012964:Sodium