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Chen R, Chung SH. Structural basis of the selective block of Kv1.2 by maurotoxin from computer simulations. PLoS One 2012; 7:e47253. [PMID: 23071772 PMCID: PMC3468451 DOI: 10.1371/journal.pone.0047253] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 09/12/2012] [Indexed: 12/22/2022] Open
Abstract
The 34-residue polypeptide maurotoxin (MTx) isolated from scorpion venoms selectively inhibits the current of the voltage-gated potassium channel Kv1.2 by occluding the ion conduction pathway. Here using molecular dynamics simulation as a docking method, the binding modes of MTx to three closely related channels (Kv1.1, Kv1.2 and Kv1.3) are examined. We show that MTx forms more favorable electrostatic interactions with the outer vestibule of Kv1.2 compared to Kv1.1 and Kv1.3, consistent with the selectivity of MTx for Kv1.2 over Kv1.1 and Kv1.3 observed experimentally. One salt bridge in the bound complex of MTx-Kv1.2 forms and breaks in a simulation period of 20ns, suggesting the dynamic nature of toxin-channel interactions. The toxin selectivity likely arises from the differences in the shape of the channel outer vestibule, giving rise to distinct orientations of MTx on block. Potential of mean force calculations show that MTx blocks Kv1.1, Kv1.2 and Kv1.3 with an IC50 value of 6 µM, 0.6nM and 18 µM, respectively.
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Affiliation(s)
- Rong Chen
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- * E-mail: (RC); (S-HC)
| | - Shin-Ho Chung
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia
- * E-mail: (RC); (S-HC)
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2
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Chen ZY, Zeng DY, Hu YT, He YW, Pan N, Ding JP, Cao ZJ, Liu ML, Li WX, Yi H, Jiang L, Wu YL. Structural and functional diversity of acidic scorpion potassium channel toxins. PLoS One 2012; 7:e35154. [PMID: 22511981 PMCID: PMC3325286 DOI: 10.1371/journal.pone.0035154] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 03/09/2012] [Indexed: 12/19/2022] Open
Abstract
Background Although the basic scorpion K+ channel toxins (KTxs) are well-known pharmacological tools and potential drug candidates, characterization the acidic KTxs still has the great significance for their potential selectivity towards different K+ channel subtypes. Unfortunately, research on the acidic KTxs has been ignored for several years and progressed slowly. Principal Findings Here, we describe the identification of nine new acidic KTxs by cDNA cloning and bioinformatic analyses. Seven of these toxins belong to three new α-KTx subfamilies (α-KTx28, α-KTx29, and α-KTx30), and two are new members of the known κ-KTx2 subfamily. ImKTx104 containing three disulfide bridges, the first member of the α-KTx28 subfamily, has a low sequence homology with other known KTxs, and its NMR structure suggests ImKTx104 adopts a modified cystine-stabilized α-helix-loop-β-sheet (CS-α/β) fold motif that has no apparent α-helixs and β-sheets, but still stabilized by three disulfide bridges. These newly described acidic KTxs exhibit differential pharmacological effects on potassium channels. Acidic scorpion toxin ImKTx104 was the first peptide inhibitor found to affect KCNQ1 channel, which is insensitive to the basic KTxs and is strongly associated with human cardiac abnormalities. ImKTx104 selectively inhibited KCNQ1 channel with a Kd of 11.69 µM, but was less effective against the basic KTxs-sensitive potassium channels. In addition to the ImKTx104 toxin, HeTx204 peptide, containing a cystine-stabilized α-helix-loop-helix (CS-α/α) fold scaffold motif, blocked both Kv1.3 and KCNQ1 channels. StKTx23 toxin, with a cystine-stabilized α-helix-loop-β-sheet (CS-α/β) fold motif, could inhibit Kv1.3 channel, but not the KCNQ1 channel. Conclusions/Significance These findings characterize the structural and functional diversity of acidic KTxs, and could accelerate the development and clinical use of acidic KTxs as pharmacological tools and potential drugs.
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Affiliation(s)
- Zong-Yun Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Dan-Yun Zeng
- Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - You-Tian Hu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Ya-Wen He
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Na Pan
- Key Laboratory of Molecular Biophysics, Ministry of Education,College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Jiu-Ping Ding
- Key Laboratory of Molecular Biophysics, Ministry of Education,College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China
| | - Zhi-Jian Cao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Mai-Li Liu
- Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China
| | - Wen-Xin Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
| | - Hong Yi
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
- * E-mail: (LJ); (HY); (YW)
| | - Ling Jiang
- Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, People's Republic of China
- * E-mail: (LJ); (HY); (YW)
| | - Ying-Liang Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China
- * E-mail: (LJ); (HY); (YW)
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Visan V, Fajloun Z, Sabatier JM, Grissmer S. Mapping of Maurotoxin Binding Sites on hKv1.2, hKv1.3, and hIKCa1 Channels. Mol Pharmacol 2004; 66:1103-12. [PMID: 15286210 DOI: 10.1124/mol.104.002774] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maurotoxin (MTX) is a potent blocker of human voltage-activated Kv1.2 and intermediate-conductance calcium-activated potassium channels, hIKCa1. Because its blocking affinity on both channels is similar, although the pore region of these channels show only few conserved amino acids, we aimed to characterize the binding sites of MTX in these channels. Investigating the pH(o) dependence of MTX block on current through hKv1.2 channels, we concluded that the block is less pH(o) - sensitive than for hIKCa1 channels. Using mutant cycle analysis and computer docking, we tried to identify the amino acids through which MTX binds to hKv1.2 and hIKCa1 channels. We report that MTX interacts with hKv1.2 mainly through six strong interactions. Lys(23) from MTX protrudes into the channel pore interacting with the GYGD motif, whereas Tyr(32) and Lys(7) interact with Val(381), Asp(363), and Glu(355), stabilizing the toxin onto the channel pore. Because only Val(381), Asp(363), and the GYGD motif are conserved in hIKCa1 channels, and the replacement of His(399) from hKv1.3 channels with a threonine makes this channel MTX-sensitive, we concluded that MTX binds to all three channels through the same amino acids. Glu(355), although important, is not essential in MTX recognition. A negatively charged amino acid in this position could better stabilize the toxin-channel interaction and could explain the pH(o) sensitivity of MTX block on current through hIKCa1 versus hKv1.2 channels.
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Affiliation(s)
- Violeta Visan
- Department of Applied Physiology, University of Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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Castle NA, London DO, Creech C, Fajloun Z, Stocker JW, Sabatier JM. Maurotoxin: a potent inhibitor of intermediate conductance Ca2+-activated potassium channels. Mol Pharmacol 2003; 63:409-18. [PMID: 12527813 DOI: 10.1124/mol.63.2.409] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Maurotoxin, a 34-amino acid toxin from Scorpio maurus scorpion venom, was examined for its ability to inhibit cloned human SK (SK1, SK2, and SK3), IK1, and Slo1 calcium-activated potassium (K(Ca)) channels. Maurotoxin was found to produce a potent inhibition of Ca(2+)-activated (86)Rb efflux (IC(50), 1.4 nM) and inwardly rectifying potassium currents (IC(50), 1 nM) in CHO cells stably expressing IK1. In contrast, maurotoxin produced no inhibition of SK1, SK2, and SK3 small-conductance or Slo1 large-conductance K(Ca) channels at up to 1 microM in physiologically relevant ionic strength buffers. Maurotoxin did inhibit (86)Rb efflux (IC(50), 45 nM) through, and (125)I-apamin binding (K(i), 10 nM) to SK channels in low ionic strength buffers (i.e., 18 mM sodium, 250 mM sucrose), which is consistent with previous reports of inhibition of apamin binding to brain synaptosomes. Under similar low ionic strength conditions, the potency for maurotoxin inhibition of IK1 increased by approximately 100-fold (IC(50), 14 pM). In agreement with its ability to inhibit recombinant IK1 potassium channels, maurotoxin was found to potently inhibit the Gardos channel in human red blood cells and to inhibit the K(Ca) in activated human T lymphocytes without affecting the voltage-gated potassium current encoded by Kv1.3. Maurotoxin also did not inhibit Kv1.1 potassium channels but potently blocked Kv1.2 (IC(50), 0.1 nM). Mutation analysis indicates that similar amino acid residues contribute to the blocking activity of both IK1 and Kv1.2. The results from this study show that maurotoxin is a potent inhibitor of the IK1 subclass of K(Ca) potassium channels and may serve as a useful tool for further defining the physiological role of this channel subtype.
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Affiliation(s)
- N A Castle
- Icagen Inc., Durham, North Carolina 27703, USA.
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Fajloun Z, Ferrat G, Carlier E, M'Barek S, Regaya I, Fathallah M, Rochat H, Darbon H, de Waard M, Sabatier JM. Synthesis, 3-D structure, and pharmacology of a reticulated chimeric peptide derived from maurotoxin and Tsk scorpion toxins. Biochem Biophys Res Commun 2002; 291:640-8. [PMID: 11855838 DOI: 10.1006/bbrc.2002.6496] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Maurotoxin (MTX) is a 34-mer scorpion toxin cross-linked by four disulfide bridges that acts on both Ca(2+)-activated (SK) and voltage-gated (Kv) K(+) channels. A 38-mer chimera of MTX, Tsk-MTX, has been synthesized by the solid-phase method. It encompasses residues from 1 to 6 of Tsk at N-terminal, and residues from 3 to 34 of MTX at C-terminal. As established by enzyme cleavage, Tsk-MTX displays half-cystine pairings of the type C1-C5, C2-C6, C3-C7 and C4-C8 which, contrary to MTX, correspond to a disulfide bridge pattern common to known scorpion toxins. The 3-D structure of Tsk-MTX, solved by (1)H NMR, demonstrates that it adopts the alpha/beta scaffold of scorpion toxins. In vivo, Tsk-MTX is lethal by intracerebroventricular injection in mice (LD(50) value of 0.2 microg/mouse). In vitro, Tsk-MTX is as potent as MTX, or Tsk, to interact with apamin-sensitive SK channels of rat brain synaptosomes (IC(50) value of 2.5 nM). It also blocks voltage-gated K(+) channels expressed in Xenopus oocytes, but is inactive on rat Kv1.3 contrary to MTX.
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Affiliation(s)
- Ziad Fajloun
- Boulevard Pierre Dramard, CNRS UMR 6560, 13916 Marseille Cedex 20, France
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Carlier E, Fajloun Z, Mansuelle P, Fathallah M, Mosbah A, Oughideni R, Sandoz G, Di Luccio E, Geib S, Regaya I, Brocard J, Rochat H, Darbon H, Devaux C, Sabatier JM, de Waard M. Disulfide bridge reorganization induced by proline mutations in maurotoxin. FEBS Lett 2001; 489:202-7. [PMID: 11165250 DOI: 10.1016/s0014-5793(00)02433-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Maurotoxin (MTX) is a 34-residue toxin that has been isolated from the venom of the chactidae scorpion Scorpio maurus palmatus, and characterized. Together with Pi1 and HsTx1, MTX belongs to a family of short-chain four-disulfide-bridged scorpion toxins acting on potassium channels. However, contrary to other members of this family, MTX exhibits an uncommon disulfide bridge organization of the type C1-C5, C2-C6, C3-C4 and C7-C8, versus C1-C5, C2-C6, C3-C7 and C4-C8 for both Pi1 and HsTx1. Here, we report that the substitution of MTX proline residues located at positions 12 and/or 20, adjacent to C3 (Cys(13)) and C4 (Cys(19)), results in conventional Pi1- and HsTx1-like arrangement of the half-cystine pairings. In this case, this novel disulfide bridge arrangement is without obvious incidence on the overall three-dimensional structure of the toxin. Pharmacological assays of this structural analog, [A(12),A(20)]MTX, reveal that the blocking activities on Shaker B and rat Kv1.2 channels remain potent whereas the peptide becomes inactive on rat Kv1.3. These data indicate, for the first time, that discrete point mutations in MTX can result in a marked reorganization of the half-cystine pairings, accompanied with a novel pharmacological profile for the analog.
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Affiliation(s)
- E Carlier
- Laboratoire de Neurobiologie des Canaux Ioniques, INSERM U464, IFR Jean Roche, Marseille, France
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Fajloun Z, Mosbah A, Carlier E, Mansuelle P, Sandoz G, Fathallah M, di Luccio E, Devaux C, Rochat H, Darbon H, De Waard M, Sabatier JM. Maurotoxin versus Pi1/HsTx1 scorpion toxins. Toward new insights in the understanding of their distinct disulfide bridge patterns. J Biol Chem 2000; 275:39394-402. [PMID: 10970898 DOI: 10.1074/jbc.m006810200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Maurotoxin (MTX) is a scorpion toxin acting on several K(+) channel subtypes. It is a 34-residue peptide cross-linked by four disulfide bridges that are in an "uncommon" arrangement of the type C1-C5, C2-C6, C3-C4, and C7-C8 (versus C1-C5, C2-C6, C3-C7, and C4-C8 for Pi1 or HsTx1, two MTX-related scorpion toxins). We report here that a single mutation in MTX, in either position 15 or 33, resulted in a shift from the MTX toward the Pi1/HsTx1 disulfide bridge pattern. This shift is accompanied by structural and pharmacological changes of the peptide without altering the general alpha/beta scaffold of scorpion toxins.
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Affiliation(s)
- Z Fajloun
- CNRS UMR 6560, Boulevard Pierre Dramard, 13916 Marseille Cedex 20, the Architecture et Fonction des Macromolécules Biologiques, CNRS UPR 9039, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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Fajloun Z, Carlier E, Lecomte C, Geib S, Di Luccio E, Bichet D, Mabrouk K, Rochat H, De Waard M, Sabatier JM. Chemical synthesis and characterization of Pi1, a scorpion toxin from Pandinus imperator active on K+ channels. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:5149-55. [PMID: 10931199 DOI: 10.1046/j.1432-1327.2000.01577.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pi1 is a 35-residue toxin cross-linked by four disulfide bridges that has been isolated from the venom of the chactidae scorpion Pandinus imperator. Due to its very low abundance in the venom, we have chemically synthesized this toxin in order to study its biological activity. Enzyme-based proteolytic cleavage of the synthetic Pi1 (sPi1) demonstrates half-cystine pairings between Cys4-Cys25, Cys10-Cys30, Cys14-Cys32 and Cys20-Cys35, which is in agreement with the disulfide bridge organization initially reported on the natural toxin. In vivo, intracerebroventricular injection of sPi1 in mice produces lethal effects with an LD50 of 0.2 microgram per mouse. In vitro, the application of sPi1 induces drastic inhibition of Shaker B (IC50 of 23 nM) and rat Kv1.2 channels (IC50 of 0.44 nM) heterologously expressed in Xenopus laevis oocytes. No effect was observed on rat Kv1.1 and Kv1.3 currents upon synthetic peptide application. Also, sPi1 is able to compete with 125I-labeled apamin for binding onto rat brain synaptosomes with an IC50 of 55 pM. Overall, these results demonstrate that sPi1 displays a large spectrum of activities by blocking both SK- and Kv1-types of K+ channels; a selectivity reminiscent of that of maurotoxin, another structurally related four disulfide-bridged scorpion toxin that exhibits a different half-cystine pairing pattern.
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Affiliation(s)
- Z Fajloun
- Laboratoire de Biochimie, CNRS UMR 6560 and Laboratoire de Neurobiologie des Canaux Ioniques, INSERM U464, IFR Jean Roche, Faculté de Médecine Nord, Marseille, France.
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