The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Kenton J. Swartz - One of the best experts on this subject based on the ideXlab platform.
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Opening the shaker K+ channel with Hanatoxin.
The Journal of general physiology, 2013Co-Authors: Mirela Milescu, Chanhyung Bae, Jae Il Kim, Hwa C. Lee, Kenton J. SwartzAbstract:Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of Hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of Hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that Hanatoxin shifts the conductance–voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin–channel interaction with mutations in the S3b helix of the S1-S4 domain enhances toxin affinity and causes large shifts in the conductance–voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that Hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b–S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that the actions of tarantula toxins are not simply a product of where they bind to the channel, but that fine structural details of the toxin–channel interface determine whether a toxin is an inhibitor or opener.
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Opening the Shaker Kv Channel with Hanatoxin
Biophysical Journal, 2013Co-Authors: Mirela Milescu, Hwa Lee, Chanhyung Bae, Jae Il Kim, Kenton J. SwartzAbstract:Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1-S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of Hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1-S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of Hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that Hanatoxin shifts the conductance-voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin-channel interaction with mutations in the S3b helix of the S1-S4 domain enhance toxin affinity and cause large shifts in the conductance-voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that Hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b-S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that specific interactions between toxins and paddle motifs determine whether these toxins inhibit or promote channel opening.
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Localization and Molecular Determinants of the Hanatoxin Receptors on the Voltage-Sensing Domains of a K+ Channel
The Journal of general physiology, 2000Co-Authors: Yingying Li-smerin, Kenton J. SwartzAbstract:Hanatoxin inhibits voltage-gated K+ channels by modifying the energetics of activation. We studied the molecular determinants and physical location of the Hanatoxin receptors on the drk1 voltage-gated K+ channel. First, we made multiple substitutions at three previously identified positions in the COOH terminus of S3 to examine whether these residues interact intimately with the toxin. We also examined a region encompassing S1–S3 using alanine-scanning mutagenesis to identify additional determinants of the toxin receptors. Finally, guided by the structure of the KcsA K+ channel, we explored whether the toxin interacts with the peripheral extracellular surface of the pore domain in the drk1 K+ channel. Our results argue for an intimate interaction between the toxin and the COOH terminus of S3 and suggest that the Hanatoxin receptors are confined within the voltage-sensing domains of the channel, at least 20–25 A away from the central pore axis.
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Localization and molecular determinants of the Hanatoxin receptors on the voltage-sensing domains of a K
2000Co-Authors: Yingying Li-smerin, Kenton J. SwartzAbstract:abstract Hanatoxin inhibits voltage-gated K � channels by modifying the energetics of activation. We studied the molecular determinants and physical location of the Hanatoxin receptors on the drk1 voltage-gated K � channel. First, we made multiple substitutions at three previously identified positions in the COOH terminus of S3 to examine whether these residues interact intimately with the toxin. We also examined a region encompassing S1– S3 using alanine-scanning mutagenesis to identify additional determinants of the toxin receptors. Finally, guided by the structure of the KcsA K � channel, we explored whether the toxin interacts with the peripheral extracellular surface of the pore domain in the drk1 K � channel. Our results argue for an intimate interaction between the toxin and the COOH terminus of S3 and suggest that the Hanatoxin receptors are confined within the voltagesensing domains of the channel, at least 20–25 Å away from the central pore axis. key words: gating modifier toxin • scanning mutagenesis • voltage-dependent gating • protein–protein interactio
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gating modifier toxins reveal a conserved structural motif in voltage gated ca2 and k channels
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Yingying Lismerin, Kenton J. SwartzAbstract:Protein toxins from venomous animals exhibit remarkably specific and selective interactions with a wide variety of ion channels. Hanatoxin and grammotoxin are two related protein toxins found in the venom of the Chilean Rose Tarantula, Phrixotrichus spatulata. Hanatoxin inhibits voltage-gated K+ channels and grammotoxin inhibits voltage-gated Ca2+ channels. Both toxins inhibit their respective channels by interfering with normal operation of the voltage-dependent gating mechanism. The sequence homology of Hanatoxin and grammotoxin, as well as their similar mechanism of action, raises the possibility that they interact with the same region of voltage-gated Ca2+ and K+ channels. Here, we show that each toxin can interact with both voltage-gated Ca2+ and K+ channels and modify channel gating. Moreover, mutagenesis of voltage-gated K+ channels suggests that Hanatoxin and grammotoxin recognize the same structural motif. We propose that these toxins recognize a voltage-sensing domain or module present in voltage-gated ion channels and that this domain has a highly conserved three-dimensional structure.
Y. Y. Shiau - One of the best experts on this subject based on the ideXlab platform.
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Molecular simulation reveals structural determinants of the Hanatoxin binding in Kv2.1 channels
Molecular modeling annual, 2002Co-Authors: Yu-shuan Shiau, Kuo-long Lou, H. H. Liou, T. B. Lin, Po-tsarng Huang, Y. Y. ShiauAbstract:The carboxyl terminus of the S3 segment (S3_C) in voltage-gated potassium channels was suggested to be the binding site of gating modifier toxins like Hanatoxin. It has also been proposed to have a helical secondary structural arrangement. The currently available structures in high resolution for such channel molecules are restricted to regions illustrating the pore function. Therefore no further direct experimental data to elucidate the detailed mechanism for such toxin binding can be derived. In order to examine the putative three-dimensional structure of S3_C and to analyze the residues required for Hanatoxin binding, molecular simulation and docking were performed, based on the solution structure of Hanatoxin and the structural information from mutational scanning data for the S3_C fragment in Kv2.1. Our results indicate that hydrophobic and electrostatic interactions are both utilized to stabilize the toxin binding. Precise docking residues and the appropriate orientation for binding regarding amphipathic environments are also described. Compared with the functional data proposed by previous studies, the helical structural arrangement for the C-terminus of the S3 segment in voltage-gated potassium channels can therefore be further emphasized and analyzed. The possible location/orientation for toxin binding with respect to membrane distribution around the S3_C segment is also discussed in this paper.
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Structural influence of Hanatoxin binding on the carboxyl terminus of S3 segment in voltage-gated K(+)-channel Kv2.1.
Receptors & channels, 2002Co-Authors: Po-tsang Huang, T. Y. Chen, L. J. Tseng, Kuo-long Lou, H. H. Liou, T. B. Lin, H. C. Spatz, Y. Y. ShiauAbstract:The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drkl) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3 C ) bears a gradually broader interest concerning the site for gating modifier toxins like Hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3 C and to illustrate the residues required for Hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3 C fragment. Our data suggest that several basic and acidic residues of Hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3 C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3 C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3 C upon toxin binding is presented as a possible explanation for the observed shift in Hanatoxin binding-induced gating.
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structural influence of Hanatoxin binding on the carboxyl terminus of s3 segment in voltage gated k channel kv2 1
Receptors & Channels, 2002Co-Authors: Po-tsang Huang, T. Y. Chen, L. J. Tseng, Kuo-long Lou, H. H. Liou, T. B. Lin, H. C. Spatz, Y. Y. ShiauAbstract:The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drkl) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3 C ) bears a gradually broader interest concerning the site for gating modifier toxins like Hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3 C and to illustrate the residues required for Hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3 C fragment. Our data suggest that several basic and acidic residues of Hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3 C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3 C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3 C upon toxin binding is presented as a possible explanation for the observed shift in Hanatoxin binding-induced gating.
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Molecular determinants of the Hanatoxin binding in voltage-gated K+-channel drk1.
Journal of molecular recognition : JMR, 2002Co-Authors: Kuo-long Lou, Po-tsang Huang, Yu-shuan Shiau, Y. Y. ShiauAbstract:The carboxyl terminus of S3 segment (S3C) in voltage-gated potassium channels was proposed to bear the binding site for gating modifier toxins like Hanatoxin and a helical secondary structural arrangement was suggested. Due to the lack of complete structure in high resolution for such a channel molecule, no further direct experimental data to elucidate the mechanism for their binding conformations could thus far be derived. In order to examine the putative three-dimensional structure of S3C and to illustrate the residues required for Hanatoxin binding, molecular simulation and docking were performed, based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3C fragment. From our results, it is indicated that both hydrophobic and electrostatic interactions are utilized to stabilize the toxin binding. Detailed docking residues and appropriate orientation for binding regarding hydrophobic/-philic environments are also described. Compared with the functional data proposed by previous studies, the helical structural arrangement for the C-terminus of S3 segment in voltage-gated potassium channels can therefore be further emphasized. Copyright © 2002 John Wiley & Sons, Ltd.
Mirela Milescu - One of the best experts on this subject based on the ideXlab platform.
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Opening the shaker K+ channel with Hanatoxin.
The Journal of general physiology, 2013Co-Authors: Mirela Milescu, Chanhyung Bae, Jae Il Kim, Hwa C. Lee, Kenton J. SwartzAbstract:Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of Hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of Hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that Hanatoxin shifts the conductance–voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin–channel interaction with mutations in the S3b helix of the S1-S4 domain enhances toxin affinity and causes large shifts in the conductance–voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that Hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b–S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that the actions of tarantula toxins are not simply a product of where they bind to the channel, but that fine structural details of the toxin–channel interface determine whether a toxin is an inhibitor or opener.
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Opening the Shaker Kv Channel with Hanatoxin
Biophysical Journal, 2013Co-Authors: Mirela Milescu, Hwa Lee, Chanhyung Bae, Jae Il Kim, Kenton J. SwartzAbstract:Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1-S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of Hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1-S4 domain and inhibits opening by stabilizing a closed state. Here we investigated the interaction of Hanatoxin with the Shaker Kv channel, a voltage-activated channel that has been extensively studied with biophysical approaches. In contrast to what is observed in the Kv2.1 channel, we find that Hanatoxin shifts the conductance-voltage relation to negative voltages, making it easier to open the channel with membrane depolarization. Although these actions of the toxin are subtle in the wild-type channel, strengthening the toxin-channel interaction with mutations in the S3b helix of the S1-S4 domain enhance toxin affinity and cause large shifts in the conductance-voltage relationship. Using a range of previously characterized mutants of the Shaker Kv channel, we find that Hanatoxin stabilizes an activated conformation of the voltage sensors, in addition to promoting opening through an effect on the final opening transition. Chimeras in which S3b-S4 paddle motifs are transferred between Kv2.1 and Shaker Kv channels, as well as experiments with the related tarantula toxin GxTx-1E, lead us to conclude that specific interactions between toxins and paddle motifs determine whether these toxins inhibit or promote channel opening.
Roderick Mackinnon - One of the best experts on this subject based on the ideXlab platform.
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An inhibitor of the Kv2.1 potassium channel isolated from the venom of a Chilean tarantula
Neuron, 1995Co-Authors: Kenton J. Swartz, Roderick MackinnonAbstract:The Kv2.1 voltage-activated K+ channel, a Shab-related K+ channel isolated from rat brain, is insensitive to previously identified peptide inhibitors. We have isolated two peptides from the venom of a Chilean tarantula, G. spatulata, that inhibit the Kv2.1 K+ channel. The two peptides, Hanatoxin, (HaTx1) and Hanatoxin2 (HaTx2), are unrelated in primary sequence to other K+ channel inhibitors. The activity of HaTx was verified by synthesizing it in a bacterial expression system. The concentration dependence for both the degree of inhibition at equilibrium (Kd = 42 nM) and the kinetics of inhibition (kon = 3.7 × 104 M-1s-1; koff = 1.3 × 10-3 s-1), are consistent with a bimolecular reaction between HaTx and the Kv2.1 K+ channel. Shaker-related, Shaw-related, and eag K+ channels were relatively insensitive to HaTx, whereas a Shal-related K+ channel was sensitive. Regions outside the scorpion toxin binding site (S5-S6 linker) determine sensitivity to HaTx. HaTx introduces a new class of K+ channel inhibitors that will be useful probes for studying K+ channel structure and function. © 1995.
Kuo-long Lou - One of the best experts on this subject based on the ideXlab platform.
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Molecular simulation reveals structural determinants of the Hanatoxin binding in Kv2.1 channels
Molecular modeling annual, 2002Co-Authors: Yu-shuan Shiau, Kuo-long Lou, H. H. Liou, T. B. Lin, Po-tsarng Huang, Y. Y. ShiauAbstract:The carboxyl terminus of the S3 segment (S3_C) in voltage-gated potassium channels was suggested to be the binding site of gating modifier toxins like Hanatoxin. It has also been proposed to have a helical secondary structural arrangement. The currently available structures in high resolution for such channel molecules are restricted to regions illustrating the pore function. Therefore no further direct experimental data to elucidate the detailed mechanism for such toxin binding can be derived. In order to examine the putative three-dimensional structure of S3_C and to analyze the residues required for Hanatoxin binding, molecular simulation and docking were performed, based on the solution structure of Hanatoxin and the structural information from mutational scanning data for the S3_C fragment in Kv2.1. Our results indicate that hydrophobic and electrostatic interactions are both utilized to stabilize the toxin binding. Precise docking residues and the appropriate orientation for binding regarding amphipathic environments are also described. Compared with the functional data proposed by previous studies, the helical structural arrangement for the C-terminus of the S3 segment in voltage-gated potassium channels can therefore be further emphasized and analyzed. The possible location/orientation for toxin binding with respect to membrane distribution around the S3_C segment is also discussed in this paper.
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Structural influence of Hanatoxin binding on the carboxyl terminus of S3 segment in voltage-gated K(+)-channel Kv2.1.
Receptors & channels, 2002Co-Authors: Po-tsang Huang, T. Y. Chen, L. J. Tseng, Kuo-long Lou, H. H. Liou, T. B. Lin, H. C. Spatz, Y. Y. ShiauAbstract:The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drkl) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3 C ) bears a gradually broader interest concerning the site for gating modifier toxins like Hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3 C and to illustrate the residues required for Hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3 C fragment. Our data suggest that several basic and acidic residues of Hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3 C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3 C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3 C upon toxin binding is presented as a possible explanation for the observed shift in Hanatoxin binding-induced gating.
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structural influence of Hanatoxin binding on the carboxyl terminus of s3 segment in voltage gated k channel kv2 1
Receptors & Channels, 2002Co-Authors: Po-tsang Huang, T. Y. Chen, L. J. Tseng, Kuo-long Lou, H. H. Liou, T. B. Lin, H. C. Spatz, Y. Y. ShiauAbstract:The voltage-sensing domains of voltage-gated potassium channels Kv2.1 (drkl) contain four transmembrane segments in each subunit, termed S1 to S4. While S4 is known as the voltage sensor, the carboxyl terminus of S3 (S3 C ) bears a gradually broader interest concerning the site for gating modifier toxins like Hanatoxin and thus the secondary structure arrangement as well as its surrounding environment. To further examine the putative three-dimensional (3-D) structure of S3 C and to illustrate the residues required for Hanatoxin binding (which may, in turn, show the influence on the S4 in terms of changes in channel gating), molecular simulations and dockings were performed. These were based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3 C fragment. Our data suggest that several basic and acidic residues of Hanatoxin are electrostatically and stereochemically mapped onto their partner residues on S3 C helix, whereas some aromatic or hydrophobic residues located on the same helical fragment interact with the hydrophobic patch of the toxin upon binding. Therefore, a slight distortion of the S3 C helix, in a direction toward the N-terminus of S4, may exist. Such conformational change of S3 C upon toxin binding is presented as a possible explanation for the observed shift in Hanatoxin binding-induced gating.
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Molecular determinants of the Hanatoxin binding in voltage-gated K+-channel drk1.
Journal of molecular recognition : JMR, 2002Co-Authors: Kuo-long Lou, Po-tsang Huang, Yu-shuan Shiau, Y. Y. ShiauAbstract:The carboxyl terminus of S3 segment (S3C) in voltage-gated potassium channels was proposed to bear the binding site for gating modifier toxins like Hanatoxin and a helical secondary structural arrangement was suggested. Due to the lack of complete structure in high resolution for such a channel molecule, no further direct experimental data to elucidate the mechanism for their binding conformations could thus far be derived. In order to examine the putative three-dimensional structure of S3C and to illustrate the residues required for Hanatoxin binding, molecular simulation and docking were performed, based on the solution structure of Hanatoxin and the structural information from lysine-scanning results for S3C fragment. From our results, it is indicated that both hydrophobic and electrostatic interactions are utilized to stabilize the toxin binding. Detailed docking residues and appropriate orientation for binding regarding hydrophobic/-philic environments are also described. Compared with the functional data proposed by previous studies, the helical structural arrangement for the C-terminus of S3 segment in voltage-gated potassium channels can therefore be further emphasized. Copyright © 2002 John Wiley & Sons, Ltd.
