Referenced in: none

Automatically associated channels: SK1 , SK2 , SK3 , Slo1

Title: 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.

Authors: Paola Pedarzani, Dieter D'Hoedt, Kevina B Doorty, Jonathan D F Wadsworth, Jeremiah S Joseph, Kandiah Jeyaseelan, R Manjunatha Kini, S V Gadre, S M Sapatnekar, Martin Stocker, Peter N Strong

Journal, date & volume: J. Biol. Chem., 2002 Nov 29 , 277, 46101-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/12239213

Abstract
The biophysical properties of small conductance Ca(2+)-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 I(AHP) and the Ca(2+)-activated K(+) channels mediating the slow I(AHP) (sI(AHP)) in hippocampal neurons. Compared with related scorpion toxins, tamapin displayed a unique, remarkable selectivity for SK2 versus SK1 ( approximately 1750-fold) and SK3 ( approximately 70-fold) channels and is the most potent SK2 channel blocker characterized so far (IC(50) 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.