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Dastpeyman M, Giacomin P, Wilson D, Nolan MJ, Bansal PS, Daly NL. A C-Terminal Fragment of Chlorotoxin Retains Bioactivity and Inhibits Cell Migration. Front Pharmacol 2019; 10:250. [PMID: 30949052 PMCID: PMC6435586 DOI: 10.3389/fphar.2019.00250] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 02/26/2019] [Indexed: 11/13/2022] Open
Abstract
Chlorotoxin was originally isolated from the venom of the Israeli scorpion Leiurus quinquestriatus, and has potential as a tumor imaging agent based on its selective binding to tumor cells. Several targets have been suggested for chlorotoxin including voltage-gated chloride channels, and it has been shown to have anti-angiogenic activity and inhibit cell migration. The structure of chlorotoxin is stabilized by four disulfide bonds and contains β-sheet and helical structure. Interestingly, the reduced form has previously been shown to inhibit cell migration to the same extent as the wild type, but structural analysis indicates that the reduced form of the peptide does not maintain the native secondary structure and appears unstructured in solution. This lack of structure suggests that a short stretch of amino acids might be responsible for the bioactivity. To explore this hypothesis, we have synthesized fragments of chlorotoxin without disulfide bonds. As expected for such small peptides, NMR analysis indicated that the peptides were unstructured in solution. However, the peptide corresponding to the eight C-terminal residues inhibited cell migration, in contrast to the other fragments. Our results suggest that the C-terminal region plays a critical role in the bioactivity of chlorotoxin.
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Affiliation(s)
- Mohadeseh Dastpeyman
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Paul Giacomin
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - David Wilson
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Matthew J Nolan
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Paramjit S Bansal
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Norelle L Daly
- Centre for Molecular Therapeutics, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
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Effects of Selective Substitution of Cysteine Residues on the Conformational Properties of Chlorotoxin Explored by Molecular Dynamics Simulations. Int J Mol Sci 2019; 20:ijms20061261. [PMID: 30871150 PMCID: PMC6470725 DOI: 10.3390/ijms20061261] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 03/10/2019] [Indexed: 12/27/2022] Open
Abstract
Chlorotoxin (CTX) is a 36–amino acid peptide with eight Cys residues that forms four disulfide bonds. It has high affinity for the glioma-specific chloride channel and matrix metalloprotease-2. Structural and binding properties of CTX analogs with various Cys residue substitutions with l-α-aminobutyric acid (Abu) have been previously reported. Using 4.2 µs molecular dynamics, we compared the conformational and essential space sampling of CTX and analogs with selective substitution of the Cys residues and associated disulfide bonds with either Abu or Ser. The native and substituted peptides maintained a high degree of α-helix propensity from residues 8 through 21, with the exception of substitution of the Cys5–Cys28 residues with Ser and the Cys16–Cys33 residues with Abu. In agreement with previous circular dichroism spectropolarimetry results, the C-terminal β-sheet content varied less from residues 25 through 29 and 32 through 36 and was well conserved in most analogs. The Cys16–Cys33 and Cys20–Cys35 disulfide-bonded residues appear to be required to maintain the αβ motif of CTX. Selective substitution with the hydrophilic Ser, may mitigate the destabilizing effect of Cys16–Cys33 substitution through the formation of an inter residue H-bond from Ser16:OγH to Ser33:OγH bridged by a water molecule. All peptides shared considerable sampled conformational space, which explains the retained receptor binding of the non-native analogs.
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Atamas N, Bardik V, Bannikova A, Grishina O, Lugovskoi E, Lavoryk S, Makogonenko Y, Korolovych V, Nerukh D, Paschenko V. The effect of water dynamics on conformation changes of albumin in pre-denaturation state: photon correlation spectroscopy and simulation. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.01.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Yamaguchi Y, Peigneur S, Liu J, Uemura S, Nose T, Nirthanan S, Gopalakrishnakone P, Tytgat J, Sato K. Role of individual disulfide bridges in the conformation and activity of spinoxin (α-KTx6.13), a potassium channel toxin from Heterometrus spinifer scorpion venom. Toxicon 2016; 122:31-38. [PMID: 27660193 DOI: 10.1016/j.toxicon.2016.09.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 09/15/2016] [Accepted: 09/17/2016] [Indexed: 01/01/2023]
Abstract
Spinoxin (SPX; α-KTx6.13), isolated from venom of the scorpion Heterometrus spinifer, is a K+ channel-specific peptide toxin (KTx), which adopts a cysteine-stabilized α/β scaffold that is cross-linked by four disulfide bridges (Cys1-Cys5, Cys2-Cys6, Cys3-Cys7, and Cys4-Cys8). To investigate the role of the individual disulfide bonds in the structure-activity relationship of SPX, we synthesized four SPX analogs in which each pair of cysteine residues was replaced by alanine residues. The analysis of circular dichroism spectra and inhibitory activity against Kv1.3 channels showed that the SPX analogs lacking any of three specific disulfide bonds (Cys1-Cys5, Cys2-Cys6, and Cys3-Cys7) were unable to form the native secondary structure and completely lost inhibitory activities. Thus, we conclude that Cys1-Cys5, Cys2-Cys6, and Cys3-Cys7 are required for the inhibition of the Kv1.3 channel by SPX. In contrast, the analog lacking Cys4-Cys8 retained both native secondary structure and inhibitory activity. Interestingly, one of the isomers of the analog lacking Cys1-Cys5 also showed inhibitory activities, although its inhibition was ∼18-fold weaker than native SPX. This isomer had an atypical disulfide bond pairing (Cys3-Cys4 and Cys7-Cys8) that corresponds to that of maurotoxin (MTX), another α-KTx6 family member. These results indicate that the Cys1-Cys5 and Cys2-Cys6 bonds are important for restricting the toxin from forming an atypical (MTX-type) disulfide bond pairing among the remaining four cysteine residues (Cys3, Cys4, Cys7, and Cys8) in native SPX.
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Affiliation(s)
- Yoko Yamaguchi
- Department of Environment Sciences, Fukuoka Women's University, Fukuoka, 813-8529, Japan
| | - Steve Peigneur
- Toxicology and Pharmacology, University of Leuven, Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, Leuven, 3000, Belgium
| | - Junyi Liu
- Department of Environment Sciences, Fukuoka Women's University, Fukuoka, 813-8529, Japan
| | - Shiho Uemura
- Department of Environment Sciences, Fukuoka Women's University, Fukuoka, 813-8529, Japan
| | - Takeru Nose
- Faculty of Arts and Science, Kyushu University, Fukuoka, 819-0395, Japan
| | - Selvanayagam Nirthanan
- School of Medicine, Griffith University, Gold Coast, Queensland, 4222, Australia; School of Medical Science, Griffith University, Gold Coast, Queensland, 4222, Australia; Menzies Health Institute Queensland, Gold Coast, Australia
| | - Ponnampalam Gopalakrishnakone
- Venom and Toxin Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
| | - Jan Tytgat
- Toxicology and Pharmacology, University of Leuven, Campus Gasthuisberg O&N2, Herestraat 49, P.O. Box 922, Leuven, 3000, Belgium
| | - Kazuki Sato
- Department of Environment Sciences, Fukuoka Women's University, Fukuoka, 813-8529, Japan.
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Ojeda PG, Wang CK, Craik DJ. Chlorotoxin: Structure, activity, and potential uses in cancer therapy. Biopolymers 2016; 106:25-36. [DOI: 10.1002/bip.22748] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 09/18/2015] [Accepted: 09/18/2015] [Indexed: 01/09/2023]
Affiliation(s)
- Paola G. Ojeda
- Institute for Molecular Bioscience, the University of Queensland; Brisbane QLD 4072 Australia
| | - Conan K. Wang
- Institute for Molecular Bioscience, the University of Queensland; Brisbane QLD 4072 Australia
| | - David J. Craik
- Institute for Molecular Bioscience, the University of Queensland; Brisbane QLD 4072 Australia
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Abstract
BACKGROUND Chlorotoxin is a small scorpion peptide that inhibits glioma cell migration. We investigated the importance of a major component of chlorotoxin's chemical structure - four disulfide bonds - to its tertiary structure and biological function. RESULTS Five disulfide bond analogs of chlorotoxin were synthesized, with l-α-aminobutyric acid residues replacing each or all of the disulfide bonds. Chemical oxidation and circular dichroism experiments revealed that Cys III-VII and Cys V-VIII were essential for native structure formation. Cys I-IV and Cys II-VI were important for stability of enzymatic proteolysis but not for the inhibition of human umbilical vein endothelial cell migration. CONCLUSION The disulfide bonds of chlorotoxin are important for its structure and stability and have a minor role in its activity against cell migration.
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Martinelli AH, Kappaun K, Ligabue-Braun R, Defferrari MS, Piovesan AR, Stanisçuaski F, Demartini DR, Dal Belo CA, Almeida CG, Follmer C, Verli H, Carlini CR, Pasquali G. Structure–function studies on jaburetox, a recombinant insecticidal peptide derived from jack bean (Canavalia ensiformis) urease. Biochim Biophys Acta Gen Subj 2014; 1840:935-44. [DOI: 10.1016/j.bbagen.2013.11.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 11/02/2013] [Accepted: 11/06/2013] [Indexed: 10/26/2022]
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Castellanos MM, Colina CM. Molecular Dynamics Simulations of Human Serum Albumin and Role of Disulfide Bonds. J Phys Chem B 2013; 117:11895-905. [DOI: 10.1021/jp402994r] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Maria Monica Castellanos
- Department of Materials Science
and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Coray M. Colina
- Department of Materials Science
and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Bergeron ZL, Bingham JP. Scorpion toxins specific for potassium (K+) channels: a historical overview of peptide bioengineering. Toxins (Basel) 2012. [PMID: 23202307 PMCID: PMC3509699 DOI: 10.3390/toxins4111082] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Scorpion toxins have been central to the investigation and understanding of the physiological role of potassium (K+) channels and their expansive function in membrane biophysics. As highly specific probes, toxins have revealed a great deal about channel structure and the correlation between mutations, altered regulation and a number of human pathologies. Radio- and fluorescently-labeled toxin isoforms have contributed to localization studies of channel subtypes in expressing cells, and have been further used in competitive displacement assays for the identification of additional novel ligands for use in research and medicine. Chimeric toxins have been designed from multiple peptide scaffolds to probe channel isoform specificity, while advanced epitope chimerization has aided in the development of novel molecular therapeutics. Peptide backbone cyclization has been utilized to enhance therapeutic efficiency by augmenting serum stability and toxin half-life in vivo as a number of K+-channel isoforms have been identified with essential roles in disease states ranging from HIV, T-cell mediated autoimmune disease and hypertension to various cardiac arrhythmias and Malaria. Bioengineered scorpion toxins have been monumental to the evolution of channel science, and are now serving as templates for the development of invaluable experimental molecular therapeutics.
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Affiliation(s)
- Zachary L Bergeron
- Department of Molecular Biosciences and Bioengineering, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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Kang TS, Kini RM. Structural determinants of protein folding. Cell Mol Life Sci 2009; 66:2341-61. [PMID: 19367367 PMCID: PMC11115868 DOI: 10.1007/s00018-009-0023-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 03/07/2009] [Accepted: 03/20/2009] [Indexed: 12/11/2022]
Abstract
The last several decades have seen an explosion of knowledge in the field of structural biology. With critical advances in spectroscopic techniques in examining structures of biomacromolecules, in maturation of molecular biology techniques, as well as vast improvements in computation prowess, protein structures are now being elucidated at an unprecedented rate. In spite of all the recent advances, the protein folding puzzle remains as one of the fundamental biochemical challenges. A facet to this empiric problem is the structural determinants of protein folding. What are the driving forces that pivot a polypeptide chain to a specific conformation amongst the vast conformation space? In this review, we shall discuss some of the structural determinants to protein folding that have been identified in the recent decades.
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Affiliation(s)
- Tse Siang Kang
- The Scripps Research Institute, 10550 North Torrey Pines Road GAC 1200, La Jolla, CA 92037 USA
- Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Block S4, Singapore, 117543 Singapore
| | - R. Manjunatha Kini
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Block S3 #03-17, Singapore, 117543 Singapore
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Thangudu RR, Manoharan M, Srinivasan N, Cadet F, Sowdhamini R, Offmann B. Analysis on conservation of disulphide bonds and their structural features in homologous protein domain families. BMC STRUCTURAL BIOLOGY 2008; 8:55. [PMID: 19111067 PMCID: PMC2628669 DOI: 10.1186/1472-6807-8-55] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2008] [Accepted: 12/26/2008] [Indexed: 11/22/2022]
Abstract
Background Disulphide bridges are well known to play key roles in stability, folding and functions of proteins. Introduction or deletion of disulphides by site-directed mutagenesis have produced varying effects on stability and folding depending upon the protein and location of disulphide in the 3-D structure. Given the lack of complete understanding it is worthwhile to learn from an analysis of extent of conservation of disulphides in homologous proteins. We have also addressed the question of what structural interactions replaces a disulphide in a homologue in another homologue. Results Using a dataset involving 34,752 pairwise comparisons of homologous protein domains corresponding to 300 protein domain families of known 3-D structures, we provide a comprehensive analysis of extent of conservation of disulphide bridges and their structural features. We report that only 54% of all the disulphide bonds compared between the homologous pairs are conserved, even if, a small fraction of the non-conserved disulphides do include cytoplasmic proteins. Also, only about one fourth of the distinct disulphides are conserved in all the members in protein families. We note that while conservation of disulphide is common in many families, disulphide bond mutations are quite prevalent. Interestingly, we note that there is no clear relationship between sequence identity between two homologous proteins and disulphide bond conservation. Our analysis on structural features at the sites where cysteines forming disulphide in one homologue are replaced by non-Cys residues show that the elimination of a disulphide in a homologue need not always result in stabilizing interactions between equivalent residues. Conclusion We observe that in the homologous proteins, disulphide bonds are conserved only to a modest extent. Very interestingly, we note that extent of conservation of disulphide in homologous proteins is unrelated to the overall sequence identity between homologues. The non-conserved disulphides are often associated with variable structural features that were recruited to be associated with differentiation or specialisation of protein function.
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Affiliation(s)
- Ratna R Thangudu
- Laboratoire de Biochimie et Génétique Moléculaire, Université de La Réunion, BP 7151, 15 avenue René Cassin, 97715 Saint Denis Messag Cedex 09, La Réunion, France.
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Abstract
Acid-sensing ion channels (ASICs) are neuronal non-voltage-gated cation channels that are activated when extracellular pH falls. They contribute to sensory function and nociception in the peripheral nervous system, and in the brain they contribute to synaptic plasticity and fear responses. Some of the physiologic consequences of disrupting ASIC genes in mice suggested that ASIC channels might modulate neuronal function by mechanisms in addition to their H(+)-evoked opening. Within ASIC channel's large extracellular domain, we identified sequence resembling that in scorpion toxins that inhibit K(+) channels. Therefore, we tested the hypothesis that ASIC channels might inhibit K(+) channel function by coexpressing ASIC1a and the high-conductance Ca(2+)- and voltage-activated K(+) (BK) channel. We found that ASIC1a associated with BK channels and inhibited their current. Reducing extracellular pH disrupted the association and relieved the inhibition. BK channels, in turn, altered the kinetics of ASIC1a current. In addition to BK, ASIC1a inhibited voltage-gated Kv1.3 channels. Other ASIC channels also inhibited BK, although acidosis-dependent relief of inhibition varied. These results reveal a mechanism of ion channel interaction and reciprocal regulation. Finding that a reduced pH activated ASIC1a and relieved BK inhibition suggests that extracellular protons may enhance the activity of channels with opposing effects on membrane voltage. The wide and varied expression patterns of ASICs, BK, and related K(+) channels suggest broad opportunities for this signaling system to alter neuronal function.
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Bulaj G, Olivera BM. Folding of conotoxins: formation of the native disulfide bridges during chemical synthesis and biosynthesis of Conus peptides. Antioxid Redox Signal 2008; 10:141-55. [PMID: 17961068 DOI: 10.1089/ars.2007.1856] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Conopeptides from >700 species of predatory marine Conus snails provide an impressive molecular diversity of cysteine-rich peptides. Most of the estimated 50,000-100,000 distinct conopeptides range in size from 10 to 50 amino acid residues, often with multiple posttranslational modifications. The great majority contain from two to four disulfide bridges. As the biosynthetic and chemical production of this impressive repertoire of disulfide-rich peptides has been investigated, particularly the formation of native disulfide bridges, differences between in vivo and in vitro oxidative folding have become increasingly evident. In this article, we provide an overview of the molecular diversity of conotoxins with an emphasis on the cysteine patterns and disulfide frameworks. The conotoxin folding studies reviewed include regioselective and direct oxidation strategies, recombinant expression, optimization of folding methods, mechanisms of in vitro folding, and preliminary data on the biosynthesis of conotoxins in venom ducts. Despite these studies, how the cone snails efficiently produce properly folded conotoxins remains unanswered. As chemists continue to master oxidative folding techniques, insights gleaned from how conotoxins are folded in vivo will likely lead to the development of the new folding methods, as well as shed some light on fundamental mechanisms relevant to the protein folding problem.
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Affiliation(s)
- Grzegorz Bulaj
- Department of Medicinal Chemistry, College of Pharmacy, Salt Lake City, Utah 84108, USA.
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Mirshafiey A. Venom therapy in multiple sclerosis. Neuropharmacology 2007; 53:353-61. [PMID: 17583756 DOI: 10.1016/j.neuropharm.2007.05.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Revised: 04/30/2007] [Accepted: 05/03/2007] [Indexed: 11/16/2022]
Abstract
To date many people with multiple sclerosis (MS) seek complementary and alternative medicines (CAM) to treat their symptoms as an adjunct to conventionally used therapies. Among the common CAM therapies, there is a renewed interest in the therapeutic potential of venoms in MS. The efficacy of this therapeutic method remains unclear. However, venom-based therapy using bee, snakes and scorpions venom and/or sea anemones toxin has been recently developed because current investigations have identified the various components and molecular mechanism of the effects of venoms under in vitro and in vivo conditions. The aim of this review is to describe the recent findings regarding the role of venoms and their components in treatment of MS disease and that whether venom therapy could be recommended as a complementary treatment or not.
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Affiliation(s)
- Abbas Mirshafiey
- Department of Immunology, School of Public Health, Medical Sciences, University of Tehran, Box 6446, Tehran 14155, Iran.
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Jouirou B, Mouhat S, Andreotti N, De Waard M, Sabatier JM. Toxin determinants required for interaction with voltage-gated K+ channels. Toxicon 2004; 43:909-14. [PMID: 15208024 DOI: 10.1016/j.toxicon.2004.03.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Ion channel-acting toxins are mainly short peptides generally present in minute amounts in the venoms of diverse animal species such as scorpions, snakes, spiders, marine cone snails and sea anemones. Interestingly, these peptides have evolved over time on the basis of clearly distinct architectural motifs present throughout the animal kingdom, but display convergent molecular determinants and functional homologies. As a consequence of this conservation of some key determinants, it has also been evidenced that toxin targets display some common evolutionary origins. Indeed, these peptides often target ion channels and ligand-gated receptors, though other interacting molecules such as enzymes have been further evidenced. In this review, we provide an overview of some selected peptides from various animal species that act on specific K+ conducting voltage-gated ion channels. In particular, we emphasize our global analysis on the structural determinants of these molecules that are required for the recognition of a particular ion channel pore structure, a property that should be correlated to the blocking efficacy of the K+ efflux out of the cell during channel opening. A better understanding of these molecular determinants is valuable to better specify and derive useful peptide pharmacological properties.
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Affiliation(s)
- Besma Jouirou
- Laboratoire d'Ingénierie des Protéines, Faculte de Medecine Secteur Nord, CNRS FRE 2738, Bd Pierre Dramard, 13916 Marseille, France
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Inceoglu B, Lango J, Wu J, Hawkins P, Southern J, Hammock BD. Isolation and characterization of a novel type of neurotoxic peptide from the venom of the South African scorpion Parabuthus transvaalicus (Buthidae). EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:5407-13. [PMID: 11606203 DOI: 10.1046/j.0014-2956.2001.02479.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The venom of the South African scorpion Parabuthus transvaalicus was characterized using a combination of mass spectrometry and RP-HPLC separation and bioassays. The crude venom was initially separated into 10 fractions. A novel, moderately toxic but very high abundance peptide (birtoxin) of 58 amino-acid residues was isolated, identified and characterized. Each purification step was followed by bioassays and mass spectroscopy. First a C4 RP-HPLC column was used, then a C18 RP Microbore column purification resulted in > 95% purity in the case of birtoxin from a starting material of 230 microg of crude venom. About 12-14% of the D214 absorbance of the total venom as observed after the first chromatography step was composed of birtoxin. This peptide was lethal to mice at low microgram quantities and it induced serious symptoms including tremors, which lasted up to 24 h post injection, at submicrogram amounts. At least seven other fractions that showed different activities including one fraction with specificity against blowfly larvae were identified. Identification of potent components is an important step in designing and obtaining effective anti-venom. Antibodies raised against the critical toxic components have the potential to block the toxic effects and reduce the pain associated with the scorpion envenomation. The discovery of birtoxin, a bioactive long chain neurotoxin peptide with only three disulfide bridges, offers new insight into understanding the role of conserved disulfide bridges with respect to scorpion toxin structure and function.
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Affiliation(s)
- B Inceoglu
- Department of Entomology and Cancer Research Center, University of California, Davis 95616, USA
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Conticello SG, Gilad Y, Avidan N, Ben-Asher E, Levy Z, Fainzilber M. Mechanisms for evolving hypervariability: the case of conopeptides. Mol Biol Evol 2001; 18:120-31. [PMID: 11158371 DOI: 10.1093/oxfordjournals.molbev.a003786] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hypervariability is a prominent feature of large gene families that mediate interactions between organisms, such as venom-derived toxins or immunoglobulins. In order to study mechanisms for evolution of hypervariability, we examined an EST-generated assemblage of 170 distinct conopeptide sequences from the venoms of five species of marine Conus snails. These sequences were assigned to eight gene families, defined by conserved elements in the signal domain and untranslated regions. Order-of-magnitude differences were observed in the expression levels of individual conopeptides, with five to seven transcripts typically comprising over 50% of the sequenced clones in a given species. The conopeptide precursor alignments revealed four striking features peculiar to the mature peptide domain: (1) an accelerated rate of nucleotide substitution, (2) a bias for transversions over transitions in nucleotide substitutions, (3) a position-specific conservation of cysteine codons within the hypervariable region, and (4) a preponderance of nonsynonymous substitutions over synonymous substitutions. We propose that the first three observations argue for a mutator mechanism targeted to mature domains in conopeptide genes, combining a protective activity specific for cysteine codons and a mutagenic polymerase that exhibits transversion bias, such as DNA polymerase V. The high D:(n)/D:(s) ratio is consistent with positive or diversifying selection, and further analyses by intraspecific/interspecific gene tree contingency tests weakly support recent diversifying selection in the evolution of conopeptides. Since only the most highly expressed transcripts segregate in gene trees according to the feeding specificity of the species, diversifying selection might be acting primarily on these sequences. The combination of a targeted mutator mechanism to generate high variability with the subsequent action of diversifying selection on highly expressed variants might explain both the hypervariability of conopeptides and the large number of unique sequences per species.
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Affiliation(s)
- S G Conticello
- Laboratory of Molecular Neurobiology, Department of Biological Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel
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Vita C, Vizzavona J, Drakopoulou E, Zinn-Justin S, Gilquin B, Ménez A. Novel miniproteins engineered by the transfer of active sites to small natural scaffolds. Biopolymers 2000; 47:93-100. [PMID: 9692330 DOI: 10.1002/(sici)1097-0282(1998)47:1<93::aid-bip10>3.0.co;2-h] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Small multidisulfide-containing proteins are attractive structural templates to produce a biologically active conformation that mimics the binding surface of natural large proteins. In particular, the structural motif that is evolutionary conserved in all scorpion toxins has a small size (30-40 amino acid residues), a great structural stability, and high permissiveness for sequence mutation. This motif is composed of a beta-sheet and an alpha-helix bridged in the interior core by three disulfides. We have used this motif successfully to transfer within its beta-sheet new functional sites, including the curaremimetic loop of a snake neurotoxin and the CDR2-like site of human CD4. Accumulated evidence indicated that the two miniproteins produced, the curaremimetic miniprotein and the CD4 mimetic, contain the alpha/beta fold that is characteristic of the scaffold used and bind respectively to the acetylcholine receptor and to the envelope gp120 of HIV-1. Furthermore, the latter was shown to prevent viral infection of lymphocytes. These examples illustrate that, by the transfer of active sites to small and stable natural scaffolds, it is possible to engineer miniproteins reproducing, in part, the function of much larger proteins. Such miniproteins may be of great utility as tools in structure-function studies and as leads in drug design.
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Affiliation(s)
- C Vita
- CEA Saclay, Département d'Ingénierie et d'Etudes des Protéines, Gif-sur-Yvette, France
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Flinn JP, Pallaghy PK, Lew MJ, Murphy R, Angus JA, Norton RS. Role of disulfide bridges in the folding, structure and biological activity of omega-conotoxin GVIA. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1434:177-90. [PMID: 10556572 DOI: 10.1016/s0167-4838(99)00165-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Omega-Conotoxin GVIA (GVIA), an N-type calcium channel blocker from the cone shell Conus geographus, is a 27 residue polypeptide cross-linked by three disulfide bonds. Here, we report the synthesis, structural analysis by (1)H NMR and bioassay of analogues of GVIA with disulfide bridge deletions and N- and C-terminal truncations. Two analogues that retain the crucial Lys-2 and Tyr-13 residues in loops constrained by two native disulfide bridges were synthesised using orthogonal protection of cysteine residues. In the first analogue, the Cys-15-Cys-26 disulfide bridge was deleted (by replacing the appropriate Cys residues with Ser), while in the second, this disulfide bridge and the eight C-terminal residues were deleted. No activity was detected for either analogue in a rat vas deferens assay, which measures N-type calcium channel activity in sympathetic nerve, and NMR studies showed that this was due to a gross loss of secondary and tertiary structure. Five inactive analogues that were synthesised without orthogonal protection of Cys residues as part of a previous study (Flinn et al. (1995) J. Pept. Sci. 1, 379-384) were also investigated. Three had single disulfide deletions (via Ser substitutions) and two had N- or C-terminal deletions in addition to the disulfide deletion. Peptide mapping and NMR analyses demonstrated that at least four of these analogues had non-native disulfide pairings, which presumably accounts for their lack of activity. The NMR studies also showed that all five analogues had substantially altered tertiary structures, although the backbone chemical shifts and nuclear Overhauser enhancements (NOEs) implied that native-like turn structures persisted in some of these analogues despite the non-native disulfide pairings. This work demonstrates the importance of the disulfides in omega-conotoxin folding and shows that the Cys-15-Cys-26 disulfide is essential for activity in GVIA. The NMR analyses also emphasise that backbone chemical shifts and short- and medium-range NOEs are dictated largely by local secondary structure elements and are not necessarily reliable monitors of the tertiary fold.
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Affiliation(s)
- J P Flinn
- Biomolecular Research Institute, 343 Royal Parade, Parkville, Vic., Australia
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21
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Karczmar AG. Conclusions and comments. Xth International Symposium on Cholinergic Mechanisms. JOURNAL OF PHYSIOLOGY, PARIS 1998; 92:393-400. [PMID: 9789844 DOI: 10.1016/s0928-4257(99)80012-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ancient medicine men of Egypt and Arabia employed, under another name, the cholinergic agents, as did the hunters, warriors and shamans of Africa and South America. An explosion of cholinergic science occurred in the last and the current century, and the ISCMs witnessed and catalyzed this progress. The Xth ISCM emphasized the molecular characteristics of the receptors, cholinesterase and of the system engaged in liberation of Ach.
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Affiliation(s)
- A G Karczmar
- Research Services, Hines VA Hospital, Illinois 60141, USA
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