title: Heteropoda toxin 2 is a gating modifier toxin specific for voltage-gated K+ channels of the Kv4 family.
abstract: Kv4 voltage-gated K(+) channels are responsible for transient K(+) currents in the central nervous system and in the heart. HpTx2 is a peptide toxin that selectively inhibits these currents; making it a useful probe for understanding Kv4 channel structure and drug binding. Therefore, we developed a method to produce large amounts of recombinant HpTx2. Recombinant toxin inhibits all three Kv4 isoforms to the same degree; however, the voltage-dependence of inhibition is less apparent for Kv4.1 than for Kv4.3. Similarly, recombinant HpTx2(GS) effects gating characteristics of both channels, but Kv4.1 to a much lesser degree. The toxin lacks affinity for Kv1.4, Kv2.1, and Kv3.4. To locate the binding site, the amino acids linking the third and forth membrane spanning segments of Kv4.3 were replaced with analogous amino acids of Kv1.4. The chimeric K(+) channel was completely insensitive to block by rHpTx2, suggesting that its binding site is near the channel's voltage sensor. These data show that rHpTx2(GS) is a gating modifier toxin that binds to a site remote from the pore.
authors.affiliation: Department of Physiology and Biophysics, University at Buffalo-SUNY, 124 Sherman Hall, Buffalo, NY 14214, USA.
authors.forename: Vladislav V
authors.initials: VV
authors.lastname: Zarayskiy
authors.forename: Ganesh
authors.initials: G
authors.lastname: Balasubramanian
authors.forename: Vladimir E
authors.initials: VE
authors.lastname: Bondarenko
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Morales
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D004926:Escherichia coli; D015640:Ion Channel Gating / Q000187:drug effects*; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D009865:Oocytes / Q000187:drug effects; D010957:Plasmids / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism* / Q000633:toxicity; D016415:Sequence Alignment; D051672:Shal Potassium Channels; D013111:Spider Venoms / Q000378:metabolism* / Q000633:toxicity; D013112:Spiders / Q000737:chemistry*; D014981:Xenopus
chemical_list: D009841:Oligonucleotides; D024642:Potassium Channels, Voltage-Gated; D011994:Recombinant Proteins; D051672:Shal Potassium Channels; D013111:Spider Venoms