K_V1.3 belongs to the Shaker family of voltage-dependent K⁺ channels. The channel, encoded by KCNA3, is widely expressed in the brain, lung and osteoclasts and in several cell populations of hematopoietic origin. The prominence of K_V1.3 channels in these cells (particularly in T lymphocytes) directed much research attention. It was found that K_V1.3 is the main channel responsible for maintaining the resting potential in quiescent cells and regulating the Ca²⁺ signaling that is indispensable for normal T lymphocyte activation.^1,2 Based on the central role of K_V1.3 in regulating the initiation of an immune response, the channel has been recognized as a potential target for immunosuppressant drugs.¹

K_V1.3 channels are potently inhibited by several venomous peptide toxins among them Charybdotoxin (2.6 nM), Noxiustoxin (1 nM), Kaliotoxin (0.65 nM), Margatoxin (0.05 nM), Agitoxin-1 (1.7 nM), Agitoxin-2 (0.004 nM), Hongotoxin-1 (0.09 nM)  and Stichodactyla toxin (0.01 nM).^3-7