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Tamapin, a venom peptide from the Indian red scorpion (mesobuthus tamulus) that targets small conductance Ca2+-activated K+ channels and afterhyperpolarization currents in central neurons

By P. Pedarzani, D. D'hoedt, K. B. Doorty, J. D. F. Wadsworth, J. S. Joseph, K. Jeyaseelan, R. M. Kini, S. V. Gadre, S. M. Sapatnekar, M. Stocker and Peter Strong

Abstract

<p>The biophysical properties of small conductance Ca2+-activated K+ (SK) channels are well suited to underlie afterhyperpolarizations (AHPs) shaping the firing patterns of a conspicuous number of central and peripheral neurons. We have identified a new scorpion toxin (tamapin) that binds to 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. This toxin distinguished between the SK channels underlying the apamin-sensitive IAHP and the Ca2+-activated K+ channels mediating the slow IAHP (sIAHP) in hippocampal neurons. Compared with related scorpion toxins, tamapin displayed a unique, remarkable selectivity for SK2 versus SK1 (~1750-fold) and SK3 (~70-fold) channels and is the most potent SK2 channel blocker characterized so far (IC50 for SK2 channels = 24 pM). Tamapin will facilitate the characterization of the subunit composition of native SK channels and help determine their involvement in electrical and biochemical signaling.</p

Publisher: American Society for Biochemistry and Molecular Biology
Year: 2002
DOI identifier: 10.1074/jbc.m206465200
OAI identifier: oai:shura.shu.ac.uk:428
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