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. It is in these cells (particularly T lymphocytes) that K_V1.3 function has centered a lot of 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 (#STC-325, 2.6 nM), Noxiustoxin (#STN-340, 1 nM), Kaliotoxin (#STK-370, 0.65 nM), Margatoxin (#STM-325, 0.05 nM), Agitoxin-1 (#STA-150, 1.7 nM), Agitoxin-2 (#STA-420, 0.004 nM), Hongotoxin-1 (#RTH-400, 0.09 nM)  and Stichodactyla toxin (#STS-400, 0.01 nM).^3-7