Discrepin, a new peptide of the sub-family α-ktx15, isolated from the scorpion Tityus discrepans irreversibly blocks K+-channels (IA currents) of cerebellum granular cells

A new peptide was purified from the venom of the Venezuelan scorpion Tityus discrepans, by high-performance liquid chromatography and its amino acid sequence was completed by Edman degradation and mass spectrometry analysis. It contains 38 amino acid residues with a molecular weight of 4177.7 atomic mass units, tightly folded by three disulfide bridges, and has a pyroglutamic acid at the N-terminal region. This peptide, named Discrepin, was shown to block preferentially the IA currents of the voltage-dependent K+-channel of rat cerebellum granular cells in culture. The K+-currents are inhibited in an apparently irreversible manner, whose 50% inhibitory effect is reached with a 190 nM toxin concentration. The systematic nomenclature proposed for this toxin is α-KTx15.6.