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 microM for the toxin-channel complex.
Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 486, 30161-970, MG, Belo Horizonte, Brazil.
Alessandra
A
Matavel
Jader S
JS
Cruz
Claudia L
CL
Penaforte
Demétrius A M
DA
Araújo
Evanguedes
E
Kalapothakis
Vânia F
VF
Prado
Carlos R
CR
Diniz
Marta N
MN
Cordeiro
Paulo S L
PS
Beirão
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000032:analysis; D004553:Electric Conductivity; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000235:genetics / Q000494:pharmacology*; D010455:Peptides / Q000235:genetics / Q000494:pharmacology; D011892:Rana catesbeiana; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013111:Spider Venoms / Q000235:genetics / Q000494:pharmacology; D013112:Spiders / Q000737:chemistry* / Q000235:genetics
D018076:DNA, Complementary; D007473:Ion Channels; D009479:Neuropeptides; D010455:Peptides; D015222:Sodium Channels; D013111:Spider Venoms; C540367:Tx2-6 protein, Phoneutria nigriventer; C076902:Tx2 neurotoxin