Inhibits voltage-gated potassium channels (IC(50)=14.42 nM for rKCNA1/Kv1.1, IC(50)=80.4 nM for rKCNA2/Kv1.2, IC(50)=7.76 nM for rKCNA6/Kv1.6, IC(50)=13.12 nM for hKCNA3/Kv1.3, and IC(50)=49.14 nM for insect Shaker IR). Binds the Shaker IR channels in a voltage-independent manner. No cytolytic activity on erythrocytes detected. Not active on rat KCNA4/Kv1.4 or KCNA5/Kv1.5 channels. Belongs to the sea anemone type 1 potassium channel toxin family. Type 1b subfamily.