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The molecular structure of the cystin knot protein family member Ptu1 reveals a 2-stranded antiparallel beta-sheet forming the secondary structure. Results demonstrate that the acidic Asp-16 residue of the loop 2 is involved in the binding of the toxin to N-type calcium-channels, although with low affinity.

Many toxins have been purified from scorpion venom. The interaction of scorpion toxins with potassium channels is well known, but the interaction of scorpion toxins with calcium-activated potassium channels BKCa and SKCa is less well known. The first two groups of toxins from the venom of the Chinese scorpion Buthus martensi, directed against potassium channels have recently been purified and characterized. One group of toxins, BmTX1, BmTX2 and BmKTX acts on the voltage-gated potassium channels. Their structures are investigated and it is demonstrated that their differences are not linked to a modified structure but to point mutations.

The venom of the Chinese scorpion Buthus martensi was purified and characterized for its content in toxins active on potassium ion channels. The physicochemical characterization of three toxins from Buthus martensi as well as their pharmacological properties toward the potassium ion channels were described. Results showed that the toxins are lethal neurotoxic agents in mice and potent inhibitors of the voltage-gated potassium ion channels.

A delta-palutoxin variant with the highest affinity for insect voltage-gated sodium channels (NaChs) is scanned by Ala mutagenesis the surface of delta-PaluIT2, and is compared to the bioactive surface of a scorpion beta-toxin. Spider delta-palutoxins and scorpion beta-toxins show some commonality in their bioactive surfaces, which might explain their ability to compete for an identical receptor on voltage-gated NaChs.

Cyclodextrins form inclusion complexes with guest compounds and are useful as artificial enzymes.The structure of two regioisomers were determined by isomer conversionand analysis of the 1H NMR spectra of the anhydrocyclodextrins. Conversion was done by treatment with 1 N aqueous NaOH at 40 degrees Celsius with subsequent reversed-phase column chromatographic purification. Well-defined spectral signals were observed and ROESY spectrum showed a sequential relationship of the three glucose units and three 3,6-anhydroglucose units in the derivatives.

The present study shows how nature combined a small number of chemical building blocks to synthesize the acylpolyamine toxins in the venoms of Nephilinae orb-web spiders. Considering these structures in four parts, it was possible to rationalize a way to represent the natural combinatorial chemistry involved in the synthesis of these toxins: an aromatic moiety is connected through a linker amino acid to a polyamine chain, which in turn may be connected to an optional tail. The polyamine chains were classified into seven subtypes (from A to G) depending on the way the small chemical blocks are combined. These polyamine chains may be connected to one of the three possible chromophore moieties: 2,4- dihydroxyphenyl acetic acid, or 4-hydroxyindole acetic acid, or even with the indole acetic group. The connectivity between the aryl moiety and the polyamine chain is usually made through an asparagine residue; optionally a tail may be attached to the polyamine chain; nine different types of tails were identified among the 72 known acylpolyamine toxin structures. The combinations of three chromophores, two types of amino acid linkers, seven sub-types of polyamine backbone, and nine options of tails results in 378 different structural possibilities. However, we detected only 91 different toxin structures, which may represent the most successful structural trials in terms of efficiency of prey paralysis/death. [ABSTRACT FROM AUTHOR]

Examines a cloned Caenorhabditis elegans cDNA encoding a new insulin/immunoglobulin-like peptide. Sequence of predicted peptide; Detection of characteristic insertion of the peptide; Similarity between predicted peptide and Ceinsulin-1.

Many kinds of venomous principles modulate physiological responses of mammalian signal transduction systems, on which they act selectively as enhancers, inhibitors or some other kind of effectors. These toxins have become useful tools for physiological research. We have characterized paralyzing toxins from the venom of spiders, scorpions, insects, jellyfishes and sea anemones in the subtropical region including the Ryukyu Islands. Venom profiles are screened by MALDI-TOF fingerprinting analysis prior to purification of the venomous components, then marked target toxins of small molecular mass (1000–5000) are characterized directly by means of mass spectrometric techniques such as Frit-FAB MS/MS, PSD/CID-TOF MS, Capil. -HPLC/Q-TOF MS/MS etc. The proteinous toxins of jellyfish or sea anemone are characterized by RT-PCR technique by the information of the cleaved peptides after the protein was hydrolyzed by appropriate peptidase and the sequence of the cleaved peptide was determined by conventional methods. The venom of Araneid spider is mainly composed of a mixture of closely related acylpolyamines. More than 90 polyamine toxins were identified from one venom sac of the Madagascan spider, Nephilengys borbonica, by Frit-Fab MS/MS employing charge remote fragmentation technique. A novel polyamine toxin was also found from the rare wondering spider, Macrothele gigas from Iriomote Island. The structure of the toxin is an analog of polyamine toxin found in trapdoor spiders. Many kinds of cystine-rich peptides showing various types of ion channel antagonism have been isolated from spiders. A series of toxins possessing the same mode of cystine knots was recently isolated from the saliva of assassin bugs, Peirates turpis, Isyndus obscurus, Agriophodrus dohrni. These toxins act as calcium channel blocker. Most of the scorpion toxins reported are from scorpions hazardous to humans, and they belong to the major super family Buthoidea. Among them are the well-known genera, such as Buthus, Androctonus, Centruroides, Leiurus, or Tytius. We have investigated the minor group of scorpions from the super family Chactoidea (Scorpionidae, Ishnuridae). The venoms of these scorpions, involving the genera Heterometrus, Pandinus, Opisthacanthus, and Isometrus, contain different kinds of peptide toxins. Fingerprinting peptide analysis of the toxin profiles for these scorpions showed some difference from the profiles of Buthoidea scorpions. These venoms contain linear pore-forming peptides and 2-cystine-bridged toxins in addition to 4-cystine-bridged toxins. The most hazardous jellyfish in Okinawa, Chiropsalmus quadrigatus, and the related box jellyfishes, Carybdea rastoni, C. alata, contain quite labile proteinaceous toxins, CqTX, CrTX and CaTX, respectively. The toxins were inactivated by adding an organic solvent such as methanol or acetonitrile, by changing the pH of the toxin solution, dialyzing the toxin solution, storing the toxin in a refrigerator, or by lyophilizing the toxin solution. However, the toxic activity was retained in the presence of sodium chloride. We purified the jellyfish toxins by adding sodium chloride through all steps of the purification procedure and finally obtained the whole primary amino acid sequence of the toxin by RT-PCR method. The toxic protein CqTX is homologous to the other box jelly fish toxin, CrTX and CaTX. These toxins belong to a new class of proteins since they show no homology to known proteins. Another notorious and dangerous specimen in the Ryukyu Islands is Phyllodiscus semori. The venom is composed of three kinds of proteins (PsTX-20A, PsTX-60A, PsTX-60B). PsTX-20A shows homology to the proteinaceous toxin actinoporin, a cytolytic protein isolated from the genus Actinia, but PsTX-60s has no homology to any ever cloned proteins. Further elucidation of the mechanism of toxic action of these Coelenterates is in progress. [ABSTRACT FROM AUTHOR]

Six peptide toxins (Magi 1–6) were isolated from the Hexathelidae spider Macrothele gigas. The amino acid sequences of Magi 1, 2, 5 and 6 have low similarities to the amino acid sequences of known spider toxins. The primary structure of Magi 3 is similar to the structure of the palmitoylated peptide named PlTx-II from the North American spider Plectreurys tristis (Plectreuridae). Moreover, the amino acid sequence of Magi 4, which was revealed by cloning of its cDNA, displays similarities to the Na+ channel modifier δ-atracotoxin from the Australian spider Atrax robustus (Hexathelidae). Competitive binding assays using several 125I-labelled peptide toxins clearly demonstrated the specific binding affinity of Magi 1–5 to site 3 of the insect sodium channel and also that of Magi 5 to site 4 of the rat sodium channel. Only Magi 6 did not compete with the scorpion toxin LqhαIT in binding to site 3 despite high toxicity on lepidoptera larvae of 3.1 nmol/g. The Kis of other toxins were between 50 pM for Magi 4 and 1747 nM for Magi 1. In addition, only Magi 5 binds to both site 3 in insects (Ki=267 nM) and site 4 in rat brain synaptosomes (Ki=1.2 nM), whereas it showed no affinities for either mammal binding site 3 or insect binding site 4. Magi 5 is the first spider toxin with binding affinity to site 4 of a mammalian sodium channel. [Copyright &y& Elsevier]