These monosubstituted analogs of ShK toxin, a class of K channel blocking peptide toxins derived from the sea anemone Stichodactyla helianthus, were prepared in order to identify functionally important residues. Hereby it has been shown that the location of Lys²² within a helical structure represents a unique difference between the interactive surfaces of the sea anemone and scorpion toxins.

ShK-toxin, originally isolated from the sea anemone Stichodactyla helianthus, has been found to inhibit the specific binding of dendrotoxin I to rat brain membranes. Due to its unique structure (it contains three intramolecular disulfide bridges) and high affinity for some potassium channels, ShK-toxin may become a useful molecular probe for investigating potassium channels.