Tamapin

Tamapin is a peptide toxin isolated from the venom of the Indian red scorpion Mesobuthus Tamulus. Tamapin is amidated at its C-terminal tyrosine residue. Tamapin binds to small conductance Ca2+-activated K+ channels (SK channels) with high affinity and inhibits SK channel-mediated currents in pyramidal neurons of the hippocampus as well as in cell lines expressing distinct SK channel subunits. Contrary to Apamin or Leiurotoxin-1 (Scyllatoxin), Tamapin is an excellent toxin to discriminate among SK channel subtypes because it presents different affinities for SK1 (42 nM), SK2 (24 pM) and SK3 (1.7 nM) channels. This toxin is also the most potent SK2 channel blocker characterized so far (IC50 for SK2 channels = 24 pM) .