Potently and selectively inhibits voltage-gated potassium channels Kv11/KCNH/ERG. Acts as a gating-modifier toxin that shifts the voltage-dependence of ERG activation in the positive direction and suppresses its current amplitudes elicited by strong depolarizing pulses that maximally activate the channels. Shows significant expression differences between stressed and unstressed A.elegantissima. Belongs to the sea anemone type 3 (BDS) potassium channel toxin family.