a highly selective blocker of the high conductance Ca²⁺-activated K⁺ channel. Iberiotoxin appears to modulate ChTX binding by an allosteric mechanism.

37-amino acid peptide with 3 disulfide bridges. Synthetic ‚ originally from Buthus tamulus scorpion venom.

As a specific blocker of Ca²⁺-activated K⁺ channels‚ Iberiotoxin does not affect other types of voltage-dependent K⁺ channels which are sensitive to inhibition by Charybdotoxin.
IIberiotoxin blocks Ca²⁺-activated K⁺ channels by binding to their external mouth‚ and this binding is tighter and with an equilibrium dissociation constant 10-fold lower than that of Charybdotoxin.

1. Galvez et al., "Purification and characterization of a unique, potent, peptidyl probe for the high conductance calcium-activated potassium channel from venom of the scorpion Buthus tamulus." J. Biol. Chem. (1990) 265(19):11083-11090
2. Candia et al., "Mode of action of Iberiotoxin, a potent blocker of the large conductance Ca2+-activated K+ channel." Biophys. J. (1992). 63:583-590