AmmTx3

AmmTx3 is a blocker of A-type potassium channels. AmmTx3 was originally isolated from the venom of the scorpion Androctonus mauretanicus-this is a a synthetic version of the toxin. AmmTx3 binds on its target A-type potassium channel with an affinity of 66 pM in rat brain synaptosomes (Kv4 channels). As such, AmmTx3 should represent an excellent tool to study action potential firing frequency, spike initiation and waveform in excitable cells. AmmTx3 was indeed found to block A-type potassium currents from cerebellum granular cells and from striatum neurons but with IC50 values of 130 nM. AmmTx3 appears to be a pore blocker of Kv4.2 and Kv4.3 and seems to require the expression of the Kv4 associated protein DPP6. It should also contribute to our understanding of learning, memory and behavior. AmmTx3 shares very high sequence homology with two other A-type potassium channel blockers, Aa1 from Androctonus australis (94%) and BmTx3 from Buthus martensi (91%), and according to binding experiments the same channel target as well. AmmTx3 is a member of the a-KTX 15 family of toxins and consist of a single chain of 37 amino acid residues, with an N-terminal pyroglutamate, cross-linked by three disulfide bridges.