The Kv1.3 voltage-gated K  channel primarily expresses in immune cells and CNS. Functional heterotetrameric channels of Kv1 subunits with different combinations are common in brain. For example, Kv1.3 subunits can associate with other Kv1.1 to Kv1.6 subunits to form heterotetrameric channels. However, the potency of the high affinity inhibitors of homotetrameric Kv1.3 for asymmetric heteromeric channels has not been systematically addressed. This information is required to assess any potential side effects of the Kv1.3-based therapy of the CNS. We found that heterotetrameric channels of Kv1.3-Kv1.x showed K_d values of Vm24 and HsTX1[R14A] between 0.06−10 nM and 0.8−8.7 nM, respectively. Vm24 has high affinity (K_d = 64 pM) for Kv1.3-Kv1.2 heterotetrameters while HsTx1[R14A] has high affinity (K_d = 830 pM) for Kv1.3-Kv1.1 heterotetramers. This significant differences in potency for heterotetramers may reflect unique interactions between the toxin and the asymmetric channels.

Gain-of-function mutations in Kv1.2 can lead to alterations in neuronal excitability and synaptic transmission, potentially contributing to neurological disorders like epilepsy. Blocking Kv1.2 channels with the specific blockers can be an effective therapeutic approach for treating conditions associated with Kv1.2 gain-of-function mutations. Of seven new peptide toxins from C. bonito which are active on Kv1 channels, we reported recently that CboK7 (αKTx 2.24) has out-standing affinity for Kv1.2 and high selectivity over Kv1.3 and Kv1.1.  CboK7 thus may serve as a template for the design of high affinity and high selectivity Kv1.2 inhibitors.