Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels

Robert S. Rogowski, John H. Collins, Thomas J. O'Neill, Thomas A. Gustafson, Taco R. Werkman, Michael A Rogawski, Todd C. Tenenholz, David J. Weber, Mordecai P. Blaustein

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

Three 35-amino acid peptide K+ channel toxins (pandinotoxins) were purified from the venom of the scorpion Pandinus imperator: the toxins are designated pandinotoxin (PiTX)-Kα, PiTX-Kβ, and PiTX-Kγ. In an 86Rb tracer flux assay on rat brain synaptosomes, all three toxins selectively blocked the component of the K+-stimulated 86Rb efflux that corresponds to a voltage-gated, rapidly inactivating (A-type) K+ current (IC50 = 6, 42, and 100 nM, respectively). These toxins blocked neither the noninactivating component of the K+-stimulated 86Rb efflux (corresponding to a delayed rectifier) nor the Ca2+-dependent component of the 86Rb efflux (i.e., a Ca2+-activated K+ current) in these terminals. PiTX-Kα, which was expressed by recombinant methods, also blocked the Kv1.2 channel expressed in fibroblasts (IC50 = 32 pM). PiTX-Kα and PiTX-Kβ have identical amino acid sequences except for the seventh amino acid: a proline in PiTX-Kα, and a glutamic acid in PiTX-Kβ. They have substantial sequence homology, especially at the carboxyl termini, with another scorpion toxin, charybdotoxin (ChTX), which blocks both the Ca2+-activated and the rapidly inactivating, K+-stimulated 86Rb efflux components in synaptosomes and the Kv1.2 channel. PiTX-Kγ, however, has much less sequence homology. Conserved in all four toxins are three identically positioned disulfide bridges; an asparagine at position 30; and positive charges at positions 27, 31, and 34 (based on ChTX numbering). PiTX-Kγ is novel in that it has a fourth pair of cysteines. The PiTX structures were computer simulated, using ChTX as a model. We speculate that the three-dimensional structures of all three PiTXs resemble that of ChTX: a β-sheet at the carboxyl terminus, containing three cysteines, is linked to the central α-helix by two disulfide bridges (C17- C35 and C13-C33) and to an extended amino-terminal fragment by the third disulfide bridge (C7-C28). Further analysis of the three-dimensional structures reveals differences that may help to explain the selectivity and affinity differences of these toxins.

Original languageEnglish (US)
Pages (from-to)1167-1177
Number of pages11
JournalMolecular Pharmacology
Volume50
Issue number5
StatePublished - Nov 1996
Externally publishedYes

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Charybdotoxin
Voltage-Gated Potassium Channels
Scorpions
Kv1.2 Potassium Channel
Disulfides
Synaptosomes
Sequence Homology
Inhibitory Concentration 50
Cysteine
Scorpion Venoms
Amino Acids
Asparagine
Proline
Glutamic Acid
Amino Acid Sequence
Fibroblasts
Peptides
Brain

ASJC Scopus subject areas

  • Pharmacology

Cite this

Rogowski, R. S., Collins, J. H., O'Neill, T. J., Gustafson, T. A., Werkman, T. R., Rogawski, M. A., ... Blaustein, M. P. (1996). Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels. Molecular Pharmacology, 50(5), 1167-1177.

Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels. / Rogowski, Robert S.; Collins, John H.; O'Neill, Thomas J.; Gustafson, Thomas A.; Werkman, Taco R.; Rogawski, Michael A; Tenenholz, Todd C.; Weber, David J.; Blaustein, Mordecai P.

In: Molecular Pharmacology, Vol. 50, No. 5, 11.1996, p. 1167-1177.

Research output: Contribution to journalArticle

Rogowski, RS, Collins, JH, O'Neill, TJ, Gustafson, TA, Werkman, TR, Rogawski, MA, Tenenholz, TC, Weber, DJ & Blaustein, MP 1996, 'Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels', Molecular Pharmacology, vol. 50, no. 5, pp. 1167-1177.
Rogowski RS, Collins JH, O'Neill TJ, Gustafson TA, Werkman TR, Rogawski MA et al. Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels. Molecular Pharmacology. 1996 Nov;50(5):1167-1177.
Rogowski, Robert S. ; Collins, John H. ; O'Neill, Thomas J. ; Gustafson, Thomas A. ; Werkman, Taco R. ; Rogawski, Michael A ; Tenenholz, Todd C. ; Weber, David J. ; Blaustein, Mordecai P. / Three new toxins from the scorpion Pandinus imperator selectively block certain voltage-gated K+ channels. In: Molecular Pharmacology. 1996 ; Vol. 50, No. 5. pp. 1167-1177.
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abstract = "Three 35-amino acid peptide K+ channel toxins (pandinotoxins) were purified from the venom of the scorpion Pandinus imperator: the toxins are designated pandinotoxin (PiTX)-Kα, PiTX-Kβ, and PiTX-Kγ. In an 86Rb tracer flux assay on rat brain synaptosomes, all three toxins selectively blocked the component of the K+-stimulated 86Rb efflux that corresponds to a voltage-gated, rapidly inactivating (A-type) K+ current (IC50 = 6, 42, and 100 nM, respectively). These toxins blocked neither the noninactivating component of the K+-stimulated 86Rb efflux (corresponding to a delayed rectifier) nor the Ca2+-dependent component of the 86Rb efflux (i.e., a Ca2+-activated K+ current) in these terminals. PiTX-Kα, which was expressed by recombinant methods, also blocked the Kv1.2 channel expressed in fibroblasts (IC50 = 32 pM). PiTX-Kα and PiTX-Kβ have identical amino acid sequences except for the seventh amino acid: a proline in PiTX-Kα, and a glutamic acid in PiTX-Kβ. They have substantial sequence homology, especially at the carboxyl termini, with another scorpion toxin, charybdotoxin (ChTX), which blocks both the Ca2+-activated and the rapidly inactivating, K+-stimulated 86Rb efflux components in synaptosomes and the Kv1.2 channel. PiTX-Kγ, however, has much less sequence homology. Conserved in all four toxins are three identically positioned disulfide bridges; an asparagine at position 30; and positive charges at positions 27, 31, and 34 (based on ChTX numbering). PiTX-Kγ is novel in that it has a fourth pair of cysteines. The PiTX structures were computer simulated, using ChTX as a model. We speculate that the three-dimensional structures of all three PiTXs resemble that of ChTX: a β-sheet at the carboxyl terminus, containing three cysteines, is linked to the central α-helix by two disulfide bridges (C17- C35 and C13-C33) and to an extended amino-terminal fragment by the third disulfide bridge (C7-C28). Further analysis of the three-dimensional structures reveals differences that may help to explain the selectivity and affinity differences of these toxins.",
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AU - Rogowski, Robert S.

AU - Collins, John H.

AU - O'Neill, Thomas J.

AU - Gustafson, Thomas A.

AU - Werkman, Taco R.

AU - Rogawski, Michael A

AU - Tenenholz, Todd C.

AU - Weber, David J.

AU - Blaustein, Mordecai P.

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N2 - Three 35-amino acid peptide K+ channel toxins (pandinotoxins) were purified from the venom of the scorpion Pandinus imperator: the toxins are designated pandinotoxin (PiTX)-Kα, PiTX-Kβ, and PiTX-Kγ. In an 86Rb tracer flux assay on rat brain synaptosomes, all three toxins selectively blocked the component of the K+-stimulated 86Rb efflux that corresponds to a voltage-gated, rapidly inactivating (A-type) K+ current (IC50 = 6, 42, and 100 nM, respectively). These toxins blocked neither the noninactivating component of the K+-stimulated 86Rb efflux (corresponding to a delayed rectifier) nor the Ca2+-dependent component of the 86Rb efflux (i.e., a Ca2+-activated K+ current) in these terminals. PiTX-Kα, which was expressed by recombinant methods, also blocked the Kv1.2 channel expressed in fibroblasts (IC50 = 32 pM). PiTX-Kα and PiTX-Kβ have identical amino acid sequences except for the seventh amino acid: a proline in PiTX-Kα, and a glutamic acid in PiTX-Kβ. They have substantial sequence homology, especially at the carboxyl termini, with another scorpion toxin, charybdotoxin (ChTX), which blocks both the Ca2+-activated and the rapidly inactivating, K+-stimulated 86Rb efflux components in synaptosomes and the Kv1.2 channel. PiTX-Kγ, however, has much less sequence homology. Conserved in all four toxins are three identically positioned disulfide bridges; an asparagine at position 30; and positive charges at positions 27, 31, and 34 (based on ChTX numbering). PiTX-Kγ is novel in that it has a fourth pair of cysteines. The PiTX structures were computer simulated, using ChTX as a model. We speculate that the three-dimensional structures of all three PiTXs resemble that of ChTX: a β-sheet at the carboxyl terminus, containing three cysteines, is linked to the central α-helix by two disulfide bridges (C17- C35 and C13-C33) and to an extended amino-terminal fragment by the third disulfide bridge (C7-C28). Further analysis of the three-dimensional structures reveals differences that may help to explain the selectivity and affinity differences of these toxins.

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