Inhibits voltage-gated potassium channels (IC(50)=405.0 nM for rKCNA1/Kv1.1, IC(50)=0.03 nM for rKCNA2/Kv1.2, IC(50)=1.31 nM for rKCNA6/Kv1.6, IC(50)=74.11 nM for hKCNA3/Kv1.3, and IC(50)=247.69 nM for insect Shaker IR). Binds the Shaker IR channels in a voltage-independent manner. No cytolytic activity on erythrocytes detected. Not active on rKv1.4/KCNA4 and rKv1.5/KCNA5 channels. Belongs to the sea anemone type 1 potassium channel toxin family. Type 1b subfamily.