ammtx3 is a specific pore blocker of kv4.2 and kv4.3 channels of mice. this high-affinity blockade depends on the expression of dipeptidyl peptidase-like proteins (dpp) dpp6 and dpp10, which are proteins that co-assemble with the alpha-subunits of kv4 channels. besides its potent ability to block kv4 channel, ammtx3 also has a small blocking effect on herg channels without alteration of the gating kinetics.