Electrophysiological characterization and molecular identification of the Phoneutria nigriventer peptide toxin PnTx2-6

A cDNA with 403 nucleotides encoding the precursor of the toxin PnTx2-6 was cloned and sequenced. Subsequent analysis revealed that the precursor begins with a signal peptide and a glutamate-rich propeptide. The succeeding peptide confirmed the reported sequence of PnTx2-6. The purified toxin exerted complex effects on Na+ current of frog skeletal muscle. There was a marked decrease of the inactivation kinetics, and a shift to hyperpolarizing potentials of both the Na+ conductance and the steady-state inactivation voltage dependences, along with a reduction of the current amplitude. The concentration dependence of the modified current suggests a K-D of 0.8 muM for the toxin-channel complex. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.