Primary structure of scorpion anti-insect toxins isolated from the venom of Leiurus quinquestriatus quinquestriatus

AbstractThe amino acid sequences of insect-selective scorpion toxins, purified from the venom of Leiurus quinquestriatus quinquestriatus, have been determined by automatic phenyl isothiocyanate degradation of the S-carboxymethylated proteins and derived proteolytic peptides. The excitatory toxin Lqq IT1 and Lqq IT1' (70 residues) show the shift of one half-cystine from an external position, which is characteristic of anti-mammal toxins, to an internal sequence position. Lqq IT2, (61 residues) displays the half-cystine residue in position 12, common to the sequence of all known antimammal toxins; it induces flaccid paralysis on insects but is non-toxic for the mouse. Lqq IT2, structurally defines a new type of anti-insect toxins from scorpion venoms. CD spectra and immunological data are in agreement with this finding

Responses of the marine diatom Thalassiosira pseudonana to changes in CO2 concentration: a proteomic approach

The concentration of CO2 in many aquatic systems is variable, often lower than the KM of the primary carboxylating enzyme Rubisco, and in order to photosynthesize efficiently, many algae operate a facultative CO2 concentrating mechanism (CCM). Here we measured the responses of a marine diatom, Thalassiosira pseudonana, to high and low concentrations of CO2 at the level of transcripts, proteins and enzyme activity. Low CO2 caused many metabolic pathways to be remodeled. Carbon acquisition enzymes, primarily carbonic anhydrase, stress, degradation and signaling proteins were more abundant while proteins associated with nitrogen metabolism, energy production and chaperones were less abundant. A protein with similarities to the Ca2+/ calmodulin dependent protein kinase II_association domain, having a chloroplast targeting sequence, was only present at low CO2. This protein might be a specific response to CO2 limitation since a previous study showed that other stresses caused its reduction. The protein sequence was found in other marine diatoms and may play an important role in their response to low CO2 concentration

Phoneutria nigriventer toxin 1: a novel statedependent inhibitor of neuronal sodium channels that interacts with mu-conotoxin binding sites

ABSTRACT A toxin was purified to homogeneity from the venom of the South American armed spider Phoneutria nigriventer and found to have a molecular mass of 8600 Da and a C-terminally amidated glycine residue. It appears to be identical to Toxin 1 (Tx1) isolated previously from this venom. Tx1 reversibly inhibited sodium currents in Chinese hamster ovary cells expressing recombinant sodium (Na v 1.2) channels without affecting their fast biophysical properties. The kinetics of inhibition of peak sodium current varied with membrane potential, with on-rates increasing and off-rates decreasing with more depolarized holding potentials in the Ϫ100 to Ϫ50 mV range. Thus, the apparent affinity of Tx1 for the channel increases as the membrane is depolarized. A mono[ 125 I]iodo-Tx1 derivative displayed high-affinity binding to a single class of sites (K D ϭ 80 pM, B max ϭ 0.43 pmol/mg protein) in rat brain membranes. Solubilized binding sites were immunoprecipitated by antibodies directed against a conserved motif in sodium channel ␣ subunits. 125 I-Tx1 binding was competitively displaced by conotoxin GIIIB (IC 50 ϭ 0.5 M) but not by 1 M tetrodotoxin. However, the inhibition of 125 I-Tx1 binding by conotoxin GIIIB was abrogated in the presence of tetrodotoxin (1 M). Patch-clamp and binding data indicate that P. nigriventer Tx1 is a novel, state-dependent sodium-channel blocker that binds to a site in proximity to pharmacological site 1, overlapping conotoxin but not tetrodotoxin binding sites

Nanobacteria Are Mineralo Fetuin Complexes

“Nanobacteria” are nanometer-scale spherical and ovoid particles which have spurred one of the biggest controversies in modern microbiology. Their biological nature has been severely challenged by both geologists and microbiologists, with opinions ranging from considering them crystal structures to new life forms. Although the nature of these autonomously replicating particles is still under debate, their role in several calcification-related diseases has been reported. In order to gain better insights on this calciferous agent, we performed a large-scale project, including the analysis of “nanobacteria” susceptibility to physical and chemical compounds as well as the comprehensive nucleotide, biochemical, proteomic, and antigenic analysis of these particles. Our results definitively ruled out the existence of “nanobacteria” as living organisms and pointed out the paradoxical role of fetuin (an anti-mineralization protein) in the formation of these self-propagating mineral complexes which we propose to call “nanons.” The presence of fetuin within renal calculi was also evidenced, suggesting its role as a hydroxyapatite nucleating factor

Glyceraldehyde-3-phosphate dehydrogenase is regulated by ferredoxin-NADP reductase in the diatom Asterionella formosa

Diatoms are a widespread and ecologically important group of heterokont algae that contribute about 20% to global productivity. Previous work has shown that regulation of key Calvin cycle enzymes in diatoms differs from that of the Plantae, and that in crude extracts, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) can be inhibited by NADPH under oxidizing conditions. Here, chromatography, mass spectrometry and sequence analysis showed that in the freshwater diatom, Asterionella formosa, GAPDH can interact with ferredoxin-NADP reductase (FNR) from the primary phase of photosynthesis, and the small chloroplast protein, CP12. In contrast, the ternary complex between GAPDH, phosphoribulokinase (PRK) and CP12, that is widespread in Plantae and cyanobacteria, was absent. Surface plasmon resonance measurements confirmed that GAPDH and FNR are able to interact. Activity measurements under oxidizing conditions, showed that NADPH can inhibit GAPDH-CP12 in the presence of FNR from A. formosa or Spinacia oleracea, explaining the earlier observed inhibition within crude extracts. Diatom plastids have distinctive attributes including the lack of the oxidative pentose phosphate pathway and so cannot produce NADPH in the dark. The observed down-regulation of GAPDH may allow NADPH to be re-routed towards other reductive processes contributing to their ecological success

Binding of 125I-fasciculin to rat brain acetylcholinesterase. The complex still binds diisopropyl fluorophosphate

International audienceIodination of fasciculin 3 (FAS3) from Dendroaspis viridis venom provided us with a fully active specific probe of fasciculin binding sites on rat brain acetylcholinesterase (AChE). Binding and inhibition are concomitant, as association and inhibition rate constants k1 and ki are identical. The 125I-FAS3.AChE complex dissociates very slowly (t 1/2 = 48 h) and is characterized by a dissociation constant, Kd, of 0.4 pM. All the specific binding of 125I-FAS3 to AChE is prevented by FAS3 as from D. angusticeps venom (Kd = 0.4, 14, and 25 pM, respectively). It is also prevented by propidium iodide, BW284C51, and d-tubocurarine, which bind to peripheral anionic sites of AChE, by Ca2+ and Mg2+, known to enhance AChE activity through an allosteric phenomenon and by acetylthiocholine concentrations which lead to excess substrate inhibition of the enzyme. Diisopropyl fluorphosphate and paroxon, which inhibit AChE by phosphorylating the catalytic serine, have no effect on either the binding rate or the number of binding sites of 125I-FAS3. O-Ethyl-S2-diisopropylaminoethyl methylphosphonothionate, however, which binds irreversibly to the AChE catalytic site but reversibly to a peripheral site, induces a 130% increase in the binding rate of 125I-FAS3, without changing the total number of 125I-FAS3 binding sites. Our results demonstrate that fasciculins bind on a peripheral site of AChE, distinct from the catalytic site and, at least partly, common with the sites on which some cationic inhibitors and the substrate in excess bind. Since phosphorylation of the catalytic serine (esteratic subsite) by [1,3-3H]diisopropyl fluorophosphate can still occur on the FAS3.AChE complex, the structural modification induced by fasciculins may affect the anionic subsite of AChE catalytic site

Conformational modulation and hydrodynamic radii of CP12 protein and its complexes probed by fluorescence correlation spectroscopy

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Role of lysine and tryptophan residues in the biological activity of toxin VII (Ts gamma) from the scorpion Tityus serrulatus

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Biochemical and Pharmacological Characterization of a Depressant Insect Toxin from the Venom of the Scorpion Buthacus arenicola

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