Journal of Bioenergetics and Biomembranes

, Volume 28, Issue 3, pp 255-267

First online:

High-conductance calcium-activated potassium channels; Structure, pharmacology, and function

  • Gregory J. KaczorowskiAffiliated withMerck Research Laboratories
  • , Hans -Günther KnausAffiliated withInstitute for Biochemical Pharmacology, University of Innsbruck
  • , Reid J. LeonardAffiliated withMerck Research Laboratories
  • , Owen B. McManusAffiliated withMerck Research Laboratories
  • , Maria L. GarciaAffiliated withMerck Research Laboratories

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High-conductance calcium-activated potassium (maxi-K) channels comprise a specialized family of K+ channels. They are unique in their dual requirement for depolarization and Ca2+ binding for transition to the open, or conducting, state. Ion conduction through maxi-K channels is blocked by a family of venom-derived peptides, such as charybdotoxin and iberiotoxin. These peptides have been used to study function and structure of maxi-K channels, to identify novel channel modulators, and to follow the purification of functional maxi-K channels from smooth muscle. The channel consists of two dissimilar subunits, α and Β. The α subunit is a member of theslo Ca2+-activated K+ channel gene family and forms the ion conduction pore. The Β subunit is a structurally unique, membrane-spanning protein that contributes to channel gating and pharmacology. Potent, selective maxi-K channel effectors (both agonists and blockers) of low molecular weight have been identified from natural product sources. These agents, together with peptidyl inhibitors and site-directed antibodies raised against α and Β subunit sequences, can be used to anatomically map maxi-K channel expression, and to study the physiologic role of maxi-K channels in various tissues. One goal of such investigations is to determine whether maxi-K channels represent novel therapeutic targets.

Key words

maxi-K channels charybdotoxin iberiotoxin smooth muscle ion channel purification slo channels Β-subunit K channel agonists K channel blockers ion channel pharmacology