A new peptide, Tc1, containing only 23 amino acids closely packed by three disulfide bridges was isolated from the Amazonian scorpion Tityus cambridgei. It blocks reversibly the Shaker B K+-channels with a K d of 65 nM and displaces binding of noxiustoxin to mouse brain synaptosome membranes. It is the shortest known peptide from scorpion venom that recognizes K+-channels and constitutes a new structural subfamily of toxin, classified as alphaKTx 13.1.
