Abstract
Charybdotoxin block of a Shaker K+ channel was studied in Xenopus oocyte macropatches. Toxin on rate increases linearly with toxin concentration in an ionic strength-dependent fashion and is competitively diminished by tetraethylammonium. On rate is insensitive to transmembrane voltage and to K+ on the opposite side of the membrane. Conversely, toxin off rate is insensitive to toxin concentration, ionic strength, and added tetraethylammonium but is enhanced by membrane depolarization or K+ (or Na+) in the trans solution. Charge neutralization of charybdotoxin Lys27, however, renders off rate voltage insensitive. Our results argue that block of voltage-gated K+ channels results from the binding of one toxin molecule, so that Lys27 enters the pore and interacts with K+ (or Na+) in the ion conduction pathway.
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- Anderson C. S., MacKinnon R., Smith C., Miller C. Charybdotoxin block of single Ca2+-activated K+ channels. Effects of channel gating, voltage, and ionic strength. J Gen Physiol. 1988 Mar;91(3):317–333. doi: 10.1085/jgp.91.3.317. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Armstrong C. M. Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons. J Gen Physiol. 1971 Oct;58(4):413–437. doi: 10.1085/jgp.58.4.413. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bontems F., Gilquin B., Roumestand C., Ménez A., Toma F. Analysis of side-chain organization on a refined model of charybdotoxin: structural and functional implications. Biochemistry. 1992 Sep 1;31(34):7756–7764. doi: 10.1021/bi00149a003. [DOI] [PubMed] [Google Scholar]
- Escobar L., Root M. J., MacKinnon R. Influence of protein surface charge on the bimolecular kinetics of a potassium channel peptide inhibitor. Biochemistry. 1993 Jul 13;32(27):6982–6987. doi: 10.1021/bi00078a024. [DOI] [PubMed] [Google Scholar]
- Giangiacomo K. M., Garcia M. L., McManus O. B. Mechanism of iberiotoxin block of the large-conductance calcium-activated potassium channel from bovine aortic smooth muscle. Biochemistry. 1992 Jul 28;31(29):6719–6727. doi: 10.1021/bi00144a011. [DOI] [PubMed] [Google Scholar]
- Giangiacomo K. M., Sugg E. E., Garcia-Calvo M., Leonard R. J., McManus O. B., Kaczorowski G. J., Garcia M. L. Synthetic charybdotoxin-iberiotoxin chimeric peptides define toxin binding sites on calcium-activated and voltage-dependent potassium channels. Biochemistry. 1993 Mar 9;32(9):2363–2370. doi: 10.1021/bi00060a030. [DOI] [PubMed] [Google Scholar]
- Gimenez-Gallego G., Navia M. A., Reuben J. P., Katz G. M., Kaczorowski G. J., Garcia M. L. Purification, sequence, and model structure of charybdotoxin, a potent selective inhibitor of calcium-activated potassium channels. Proc Natl Acad Sci U S A. 1988 May;85(10):3329–3333. doi: 10.1073/pnas.85.10.3329. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goldstein S. A., Miller C. A point mutation in a Shaker K+ channel changes its charybdotoxin binding site from low to high affinity. Biophys J. 1992 Apr;62(1):5–7. doi: 10.1016/S0006-3495(92)81760-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hoshi T., Zagotta W. N., Aldrich R. W. Biophysical and molecular mechanisms of Shaker potassium channel inactivation. Science. 1990 Oct 26;250(4980):533–538. doi: 10.1126/science.2122519. [DOI] [PubMed] [Google Scholar]
- Hoshi T., Zagotta W. N., Aldrich R. W. Two types of inactivation in Shaker K+ channels: effects of alterations in the carboxy-terminal region. Neuron. 1991 Oct;7(4):547–556. doi: 10.1016/0896-6273(91)90367-9. [DOI] [PubMed] [Google Scholar]
- MacKinnon R., Heginbotham L., Abramson T. Mapping the receptor site for charybdotoxin, a pore-blocking potassium channel inhibitor. Neuron. 1990 Dec;5(6):767–771. doi: 10.1016/0896-6273(90)90335-d. [DOI] [PubMed] [Google Scholar]
- MacKinnon R., Miller C. Functional modification of a Ca2+-activated K+ channel by trimethyloxonium. Biochemistry. 1989 Oct 3;28(20):8087–8092. doi: 10.1021/bi00446a019. [DOI] [PubMed] [Google Scholar]
- MacKinnon R., Miller C. Mechanism of charybdotoxin block of the high-conductance, Ca2+-activated K+ channel. J Gen Physiol. 1988 Mar;91(3):335–349. doi: 10.1085/jgp.91.3.335. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MacKinnon R., Miller C. Mutant potassium channels with altered binding of charybdotoxin, a pore-blocking peptide inhibitor. Science. 1989 Sep 22;245(4924):1382–1385. doi: 10.1126/science.2476850. [DOI] [PubMed] [Google Scholar]
- Miller C. Competition for block of a Ca2(+)-activated K+ channel by charybdotoxin and tetraethylammonium. Neuron. 1988 Dec;1(10):1003–1006. doi: 10.1016/0896-6273(88)90157-2. [DOI] [PubMed] [Google Scholar]
- Pardo L. A., Heinemann S. H., Terlau H., Ludewig U., Lorra C., Pongs O., Stühmer W. Extracellular K+ specifically modulates a rat brain K+ channel. Proc Natl Acad Sci U S A. 1992 Mar 15;89(6):2466–2470. doi: 10.1073/pnas.89.6.2466. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Park C. S., Hausdorff S. F., Miller C. Design, synthesis, and functional expression of a gene for charybdotoxin, a peptide blocker of K+ channels. Proc Natl Acad Sci U S A. 1991 Mar 15;88(6):2046–2050. doi: 10.1073/pnas.88.6.2046. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Park C. S., Miller C. Interaction of charybdotoxin with permeant ions inside the pore of a K+ channel. Neuron. 1992 Aug;9(2):307–313. doi: 10.1016/0896-6273(92)90169-e. [DOI] [PubMed] [Google Scholar]
- Park C. S., Miller C. Mapping function to structure in a channel-blocking peptide: electrostatic mutants of charybdotoxin. Biochemistry. 1992 Sep 1;31(34):7749–7755. doi: 10.1021/bi00149a002. [DOI] [PubMed] [Google Scholar]
- Schwarz T. L., Tempel B. L., Papazian D. M., Jan Y. N., Jan L. Y. Multiple potassium-channel components are produced by alternative splicing at the Shaker locus in Drosophila. Nature. 1988 Jan 14;331(6152):137–142. doi: 10.1038/331137a0. [DOI] [PubMed] [Google Scholar]
- Shapiro M. S., DeCoursey T. E. Permeant ion effects on the gating kinetics of the type L potassium channel in mouse lymphocytes. J Gen Physiol. 1991 Jun;97(6):1251–1278. doi: 10.1085/jgp.97.6.1251. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stampe P., Kolmakova-Partensky L., Miller C. Mapping hydrophobic residues of the interaction surface of charybdotoxin. Biophys J. 1992 Apr;62(1):8–9. doi: 10.1016/S0006-3495(92)81761-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sugg E. E., Garcia M. L., Reuben J. P., Patchett A. A., Kaczorowski G. J. Synthesis and structural characterization of charybdotoxin, a potent peptidyl inhibitor of the high conductance Ca2(+)-activated K+ channel. J Biol Chem. 1990 Nov 5;265(31):18745–18748. [PubMed] [Google Scholar]