A5083825554- Ion channel regulation and function
- Nicotinic Acetylcholine Receptors Study
- Venomous Animal Envenomation and Studies
- Neuroscience and Neuropharmacology Research
- Cardiac electrophysiology and arrhythmias
- Receptor Mechanisms and Signaling
- Insect and Pesticide Research
- Ion Channels and Receptors
- Neuroscience and Neural Engineering
- Toxin Mechanisms and Immunotoxins
- Pancreatic function and diabetes
- Neurobiology and Insect Physiology Research
- Connexins and lens biology
- Photosynthetic Processes and Mechanisms
- Mitochondrial Function and Pathology
- Plant-based Medicinal Research
- Regulation of Appetite and Obesity
- Heat shock proteins research
- Redox biology and oxidative stress
- RNA and protein synthesis mechanisms
- Healthcare and Venom Research
- Calcium signaling and nucleotide metabolism
- Spectroscopy and Quantum Chemical Studies
- Neurotransmitter Receptor Influence on Behavior
- Advanced biosensing and bioanalysis techniques
Weizmann Institute of Science
2019-2024
Tel Aviv University
2004-2014
Centre National de la Recherche Scientifique
2005
Suntory Foundation for Life Sciences
2005
Institut de Pharmacologie Moléculaire et Cellulaire
2005
Planta
2004
Abstract Venoms have evolved >100 times in all major animal groups, and their components, known as toxins, been fine-tuned over millions of years into highly effective biochemical weapons. There are many outstanding questions on the evolution toxin arsenals, such how venom genes originate, contributes to fitness venomous species, which modifications at genomic, transcriptomic, protein level drive evolution. These received particularly little attention outside snakes, cone snails,...
Scorpion α-toxins are similar in their mode of action and three-dimensional structure but differ considerably affinity for various voltage-gated sodium channels (NaChs). To clarify the molecular basis high potency α-toxin LqhαIT (from Leiurus quinquestriatus hebraeus) insect NaChs, we identified by mutagenesis key residues important activity. We have found that functional surface is composed two distinct domains: a conserved "Core-domain" formed loops connecting secondary elements molecule...
Voltage-gated sodium (Nav) channels are the molecular targets of β-scorpion toxins, which shift voltage dependence activation to more negative membrane potentials by a sensor-trapping mechanism. Molecular determinants toxin (CssIV) binding and action on rat brain located in S1-S2 (IIS1-S2) S3-S4 (IIS3-S4) extracellular linkers voltage-sensing module domain II. In IIS1-S2, mutations two amino acid residues (Glu779 Pro782) significantly altered effect reducing affinity. IIS3-S4, six positions...
Activation of voltage-gated sodium (Na(v)) channels initiates and propagates action potentials in electrically excitable cells. β-Scorpion toxins, including toxin IV from Centruroides suffusus (CssIV), enhance activation Na(V) channels. CssIV stabilizes the voltage sensor domain II its activated state via a voltage-sensor trapping mechanism. Amino acid residues required for have been identified S1-S2 S3-S4 extracellular loops II. The III are also involved action, but individual amino not...
Scorpion β-toxins affect the activation of voltage-sensitive sodium channels (NaChs). Although these toxins have been instrumental in study channel gating and architecture, little is known about their active sites. By using an efficient system for production recombinant toxins, we analyzed by point mutagenesis entire surface β-toxin, Bj-xtrIT, anti-insect selective excitatory toxin from scorpion Buthotus judaicus. Each mutant was purified toxicity binding assays, as well circular dichroism...
The scorpion alpha-toxin Lqh2 (from Leiurus quinquestriatus hebraeus) is active at various mammalian voltage-gated sodium channels (Na(v)s) and inactive insect Na(v)s. To resolve the molecular basis of this preference we used following strategy: 1) was expressed in recombinant form key residues important for activity rat brain channel rNa(v)1.2a were identified by mutagenesis. These a bipartite functional surface made conserved "core domain" (residues loops connecting secondary structure...
Av3 is a short peptide toxin from the sea anemone Anemonia viridis shown to be active on crustaceans and inactive mammals. It inhibits inactivation of Na(v)s (voltage-gated Na+ channels) like structurally dissimilar scorpion alpha-toxins type I toxins that bind receptor site-3. To examine potency mode interaction with insect Na(v)s, we established system for its expression, mutagenized it throughout, analysed in toxicity, binding electrophysiological assays. The recombinant was found highly...
Neurotoxin receptor site-3 at voltage-gated Na(+) channels is recognized by various peptide toxin inhibitors of channel inactivation. Despite extensive studies the effects these toxins, their mode interaction with remained to be described molecular level. To identify constituents that interact we exploited opposing preferences LqhαIT and Lqh2 scorpion α-toxins for insect mammalian brain channels. Construction DIV/S1-S2, DIV/S3-S4, DI/S5-SS1, DI/SS2-S6 external loops rat rNa(v)1.2a (highly...
Voltage-dependent potassium channels (K v s) gate in response to changes electrical membrane potential by coupling a voltage-sensing module with K + -selective pore. Animal toxins targeting s are classified as pore blockers, which physically plug the ion conduction pathway, or gating modifiers, disrupt voltage sensor movements. A third group of blocks an unknown mechanism via binding channel turrets. Here, we show that Conkunitzin-S1 (Cs1), peptide toxin isolated from cone snail venom, binds...
Scorpion toxins that affect sodium channel (NaCh) gating in excitable cells are divided into α‐ and β‐classes. Whereas α‐toxins have been found scorpions throughout the world, anti‐mammalian β‐toxins assigned, thus far, to ‘New World’ while anti‐insect selective (depressant excitatory) described only ‘Old World’. This distribution suggested diversification of distinct pharmacological groups occurred after separation continents, 150 million years ago. We characterized a unique toxin, Lqhβ1,...
The affinity of scorpion α‐toxins for various voltage‐gated sodium channels (Na v s) differs considerably despite similar structures and activities. It has been proposed that key bioactive residues the five‐residue‐turn (residues 8–12) C‐tail form NC domain, whose topology is dictated by a cis or trans peptide‐bond conformation between 9 10, which correlates with potency on insect mammalian Na s. We examined this hypothesis using Lqh3, an α‐like toxin from Leiurus quinquestriatus hebraeus...
Photosystem II, the oxygen-evolving complex of photosynthetic organisms, includes an intriguingly large number low molecular weight polypeptides, including PsbM. Here we describe first knock-out psbM using a transplastomic, reverse genetics approach in higher plant. Homoplastomic ΔpsbM plants exhibit photoautotrophic growth. Biochemical, biophysical, and immunological analyses demonstrate that PsbM is not required for biogenesis order photosystem II complexes. However, highly...
Gating modifiers constitute a large group of polypeptide toxins that interact with the voltage-sensing module ion channels. Among them, scorpion beta-toxins induce negative shift in voltage dependence sodium channel activation. To explain their effect, "voltage sensor trapping" model has been proposed which domain-II (DIIS4) is trapped an outward, activated position by prebound beta-toxin upon membrane depolarization. Whereas toxin effect on activation was enhanced neutralization two...
Type I sea anemone toxins are highly potent modulators of voltage-gated Na-channels (Navs) and compete with the structurally dissimilar scorpion alpha-toxins on binding to receptor site-3. Although these features provide two different probes for studying site-3 channel fast inactivation, bioactive surface has not been fully resolved. We established an efficient expression system Av2 (known as ATX II), a insecticidal toxin from Anemonia viridis (previously named A. sulcata), mutagenized it...
δ-Palutoxins from the spider Paracoelotes luctuosus (Araneae: Amaurobiidae) are 36−37 residue long peptides that show preference for insect sodium channels (NaChs) and modulate their function. Although they slow NaCh inactivation in a fashion similar to of receptor site 3 modifiers, such as scorpion α-toxins, actually bind with high affinity topologically distinct 4 β-toxins. To resolve this riddle, we scanned by Ala mutagenesis surface δ-PaluIT2, δ-palutoxin variant highest NaChs, compared...
Membrane proteins play critical physiological roles as receptors, channels, pumps, and transporters. Despite their importance, however, low expression levels often hamper the experimental characterization of membrane proteins. We present an automated web-accessible design algorithm called mPROSS (https://mPROSS.weizmann.ac.il), which uses phylogenetic analysis atomistic potential, including empirical lipophilicity scale, to improve native-state energy. As a stringent test, we apply...
In a recent note to Nature, R. MacKinnon has raised the possibility that potassium channel gating modifiers are able partition in phospholipid bilayer of neuronal membranes and by increasing their partial concentration adjacent receptor, they affect function with apparent high affinity (Lee (2004) Nature 430, 232-235). This suggestion was adopted Smith et al. (Smith, J. J., Alphy, S., Seibert, A. L., Blumenthal, K. M. (2005) Biol. Chem. 280, 11127-11133), who analyzed partitioning sodium...
Scorpion β-toxin 4 from Centruroides suffusus (Css4) enhances the activation of voltage-gated sodium channels through a voltage sensor trapping mechanism by binding activated state in domain II and stabilizing it its conformation. Here we describe antagonist partial agonist properties mutant derivative this toxin. Substitution seven different amino acid residues for Glu(15) Css4 yielded toxin derivatives with both increased decreased affinities to neurotoxin receptor site on channels....
δ‐Atracotoxins (δ‐ACTXs) from Australian funnel‐web spiders differ structurally scorpion α‐toxins (ScαTx) but similarly slow sodium current inactivation and compete for their binding to channels at receptor site‐3. Characterization of the 125 I‐labelled δ‐ACTX‐Hv1a various reveals a decrease in affinity depolarized (0 mV; K d =6.5 ± 1.4 n m ) vs.polarized (−55 =0.6 0.2 rat brain synaptosomes. The increased under conditions correlates with 4.3‐fold reduction association rate 1.8‐increase...
A second-generation antihistamine, terfenadine, is known to induce arrhythmia by blocking hERG channels. In this study, we have shown that terfenadine also inhibits the activity of G-protein-gated inwardly rectifying K+ (GIRK) channels, which regulate excitability neurons and cardiomyocytes. To clarify underlying mechanism(s), examined effects several antihistamines on GIRK channels identified structural determinant for inhibition.Electrophysiological recordings were made in Xenopus oocytes...