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Gotowa bibliografia na temat „Peptide toxin”

Autor: Grafiati

Data publikacji: 6 września 2023

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Artykuły w czasopismach na temat "Peptide toxin"

Karauzum, Hatice, i Sandip Datta. "Immunization with superantigen-derived oligopeptides protect against S. aureus bacteremia (VAC8P.1058)". Journal of Immunology 194, nr 1_Supplement (1.05.2015): 144.14. http://dx.doi.org/10.4049/jimmunol.194.supp.144.14.

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Abstract Staphylococcal superantigens are exotoxins that play a major role in disease pathogenesis. Using a T cell epitope prediction tool from the Immune Epitope Database Analysis Resource (IEDB) site, sequences within staphylococcal enterotoxin A and B (SEA, SEB) and Toxic Shock Syndrome Toxin with high affinity towards H2-Iab were identified and oligopeptides SEA_aa116-128, SEB_aa16-28 and TSST-1_aa212-224 were generated. C57BL/6 mice were immunized with a cocktail of oligopeptides or whole toxins in Al(OH)3. Serum samples from peptide-immunized mice tested positive towards individual peptides and whole toxins, however, samples from mice immunized with whole toxins did not bind to any of the peptides. To determine peptide-specific T cell response primed CD4 T cells isolated from spleens and total LNs of immunized mice were co-cultured with peptide-pulsed BMDCs and cytokine response was evaluated. Only cells of peptide-immunized mice resulted in elevated levels of IL-4, IL-5, IL-10, IL-13, GM-CSF, IFNg and TNFa, while cells obtained from whole toxin-immunized mice did not differ from baseline levels. To evaluate protective efficacy of peptides against toxin expressing strains, immunized mice were infected intravenously with MNHOCH (SEB+) or Newman (SEA+) and monitored up to 13 days. Mice that were infected with MNHOCH showed significantly extended survival compared to non-immunized mice (P=0.03). No significant difference in survival was observed when infected with strain Newman.

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Stepensky, David. "Pharmacokinetics of Toxin-Derived Peptide Drugs". Toxins 10, nr 11 (20.11.2018): 483. http://dx.doi.org/10.3390/toxins10110483.

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Toxins and venoms produced by different organisms contain peptides that have evolved to have highly selective and potent pharmacological effects on specific targets for protection and predation. Several toxin-derived peptides have become drugs and are used for the management of diabetes, hypertension, chronic pain, and other medical conditions. Despite the similarity in their composition (amino acids as the building blocks), toxin-derived peptide drugs have very profound differences in their structure and conformation, in their physicochemical properties (that affect solubility, stability, etc.), and subsequently in their pharmacokinetics (the processes of absorption, distribution, metabolism, and elimination following their administration to patients). This review summarizes and critically analyzes the pharmacokinetic properties of toxin-derived peptide drugs: (1) the relationship between the chemical structure, physicochemical properties, and the pharmacokinetics of the specific drugs, (2) the major pharmacokinetic properties and parameters of these drugs, and (3) the major pharmacokinetic variability factors of the individual drugs. The structural properties of toxin-derived peptides affect their pharmacokinetics and pose some limitations on their clinical use. These properties should be taken into account during the development of new toxin-derived peptide drugs, and for the efficient and safe use of the clinically approved drugs from this group in the individual patients.

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da Silva, Daiane Laise, Rodrigo Valladão, Emidio Beraldo-Neto, Guilherme Rabelo Coelho, Oscar Bento da Silva Neto, Hugo Vigerelli, Adriana Rios Lopes i in. "Spatial Distribution and Biochemical Characterization of Serine Peptidase Inhibitors in the Venom of the Brazilian Sea Anemone Anthopleura cascaia Using Mass Spectrometry Imaging". Marine Drugs 21, nr 9 (30.08.2023): 481. http://dx.doi.org/10.3390/md21090481.

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Sea anemones are known to produce a diverse array of toxins with different cysteine-rich peptide scaffolds in their venoms. The serine peptidase inhibitors, specifically Kunitz inhibitors, are an important toxin family that is believed to function as defensive peptides, as well as prevent proteolysis of other secreted anemone toxins. In this study, we isolated three serine peptidase inhibitors named Anthopleura cascaia peptide inhibitors I, II, and III (ACPI-I, ACPI-II, and ACPI-III) from the venom of the endemic Brazilian sea anemone A. cascaia. The venom was fractionated using RP-HPLC, and the inhibitory activity of these fractions against trypsin was determined and found to range from 59% to 93%. The spatial distribution of the anemone peptides throughout A. cascaia was observed using mass spectrometry imaging. The inhibitory peptides were found to be present in the tentacles, pedal disc, and mesenterial filaments. We suggest that the three inhibitors observed during this study belong to the venom Kunitz toxin family on the basis of their similarity to PI-actitoxin-aeq3a-like and the identification of amino acid residues that correspond to a serine peptidase binding site. Our findings expand our understanding of the diversity of toxins present in sea anemone venom and shed light on their potential role in protecting other venom components from proteolysis.

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Maillère, B., J. Cotton, G. Mourier, M. Léonetti, S. Leroy i A. Ménez. "Role of thiols in the presentation of a snake toxin to murine T cells." Journal of Immunology 150, nr 12 (15.06.1993): 5270–80. http://dx.doi.org/10.4049/jimmunol.150.12.5270.

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Abstract We isolated and characterized two T hybridomas specific for a highly stable snake toxic protein. One hybridoma, called T1C9, is I-E(d)-restricted and stimulated by both the native and reduced and carboxymethylated (RCM) toxins and by synthetic fragments containing the region 24-36. The other hybridoma, called T1B2, is I-A(d)-restricted and stimulated by the native toxin, only. Neither the RCM toxin nor any of the initial synthetic peptides used in our study could stimulate it. We show that this lack of effect is associated with the presence, in the epitope-containing fragment, of irreversible blocking groups on cysteine residues. Indeed, when the fragment 32-49 has its cysteines involved in either intra-(32-49SS) or mixed disulfides, a stimulation of T1B2 was observed. Fixed APC do not present native toxin to either hybridomas but present RCM toxin to T1C9. Strikingly, fixed APC present the peptide 32-49SS to T1B2; however, we show that this is possible only because the peptide disulfide is reduced. The thiol dependence of this epitope suggests that the native toxin can stimulate T1B2 only after disulfide reduction. This reaction may constitute a major step during the processing of the toxin and more generally of any disulfide-containing Ag.

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Bahraoui, E. M., C. Granier, J. Van Rietschoten, H. Rochat i M. el Ayeb. "Specificity and neutralizing capacity of antibodies elicited by a synthetic peptide of scorpion toxin." Journal of Immunology 136, nr 9 (1.05.1986): 3371–77. http://dx.doi.org/10.4049/jimmunol.136.9.3371.

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Abstract Polyclonal antibodies raised against a synthetic peptide (sequence 50-59) of Androctonus australis Hector toxin II can neutralize the effects of toxin II in vivo. The antigenic specificities of anti-peptide and anti-toxin antibodies were compared by competitive aqueous phase radioimmunoassay by using 125I-toxin II, chemically modified or homologous toxins, and the synthetic peptide 50-59, either free or bound to bovine serum albumin (BSA). The antipeptide and anti-toxin antibodies had a comparable high affinity for the native toxin, but anti-peptide antibodies exhibited a lower binding capacity. Anti-peptide antibodies had a higher affinity for native toxin than for the peptide 50-59 bound to BSA, used as immunogen, and were unable to recognize the free peptide. These results suggest that it is necessary to restrict the conformational freedom of the immunizing peptide in order to obtain anti-peptide antibodies with a high affinity for the toxin. The lysine residue at position 58 of toxin II, essential for toxicity, appears to be immunogenic when immunization is with peptide 50-59 bound to BSA and not with the native toxin. This residue is antigenic in the native toxin, however, as shown by the anti-peptide antibodies.

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Liao, Qingyi, Xiangjin Kong, Guoqing Luo, Xiangyue Wu, Yinping Li, Qicai Liu, Cheng Tang i Zhonghua Liu. "Molecular Diversity of Peptide Toxins in the Venom of Spider Heteropoda pingtungensis as Revealed by cDNA Library and Transcriptome Sequencing Analysis". Toxins 14, nr 2 (14.02.2022): 140. http://dx.doi.org/10.3390/toxins14020140.

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The venoms of toxic animals are chemical pools composed of various proteins, peptides, and small organic molecules used for predation and defense, in which the peptidic toxins have been intensively pursued mining modulators targeting disease-related ion channels and receptors as valuable drug pioneers. In the present study, we uncovered the molecular diversity of peptide toxins in the venom of the spider Heteropoda pingtungensis (H. pingtungensis) by using a combinatory strategy of venom gland cDNA library and transcriptome sequencing (RNA-seq). An amount of 991 high-quality expressed sequence tags (ESTs) were identified from 1138 generated sequences, which fall into three categories, such as the toxin-like ESTs (531, 53.58%), the cellular component ESTs (255, 25.73%), and the no-match ESTs (205, 20.69%), as determined by gene function annotations. Of them, 190 non-redundant toxin-like peptides were identified and can be artificially grouped into 13 families based on their sequence homology and cysteine frameworks (families A–M). The predicted mature toxins contain 2–10 cysteines, which are predicted to form intramolecular disulfide bonds to stabilize their three-dimensional structures. Bioinformatics analysis showed that toxins from H. pingtungensis venom have high sequences variability and the biological targets for most toxins are unpredictable due to lack of homology to toxins with known functions in the database. Furthermore, RP-HPLC and MALDI-TOF analyses have identified a total of 110 different peptides physically existing in the H. pingtungensis venom, and many RP-HPLC fractions showed potent inhibitory activity on the heterologously expressed NaV1.7 channel. Most importantly, two novel NaV1.7 peptide antagonists, µ-Sparatoxin-Hp1 and µ-Sparatoxin-Hp2, were characterized. In conclusion, the present study has added many new members to the spider toxin superfamily and built the foundation for identifying novel modulators targeting ion channels in the H. pingtungensis venom.

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Hyland, Caroline, Laurent Vuillard, Colin Hughes i Vassilis Koronakis. "Membrane Interaction of Escherichia coliHemolysin: Flotation and Insertion-Dependent Labeling by Phospholipid Vesicles". Journal of Bacteriology 183, nr 18 (15.09.2001): 5364–70. http://dx.doi.org/10.1128/jb.183.18.5364-5370.2001.

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ABSTRACT The 1,024-amino-acid acylated hemolysin of Escherichia coli subverts host cell functions and causes cell lysis. Both activities require insertion of the toxin into target mammalian cell membranes. To identify directly the principal toxin sequences dictating membrane binding and insertion, we assayed the lipid bilayer interaction of native protoxin, stably active toxin, and recombinant peptides. Binding was assessed by flotation of protein-liposome mixtures through density gradients, and insertion was assessed by labeling with a photoactivatable probe incorporated into the target lipid bilayer. Both the active acylated hemolysin and the inactive unacylated protoxin were able to bind and also insert. Ca2+binding, which is required for toxin activity, did not influence the in vitro interaction with liposomes. Three overlapping large peptides were expressed separately. A C-terminal peptide including residues 601 to 1024 did not interact in either assay. An internal peptide spanning residues 496 to 831, including the two acylation sites, bound to phospholipid vesicles and showed a low level of insertion-dependent labeling. In vitro acylation had no effect on the bilayer interaction of either this peptide or the full-length protoxin. An N-terminal peptide comprising residues 1 to 520 also bound to phospholipid vesicles and showed strong insertion-dependent labeling, ca. 5- to 25-fold that of the internal peptide. Generation of five smaller peptides from the N-terminal region identified the principal determinant of lipid insertion as the hydrophobic sequence encompassing residues 177 to 411, which is conserved among hemolysin-related toxins.

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GREEN, Daniel, Suzi PACE, Suzanne M. CURTIS, Magdalena SAKOWSKA, Graham D. LAMB, Angela F. DULHUNTY i Marco G. CASAROTTO. "The three-dimensional structural surface of two beta-sheet scorpion toxins mimics that of an alpha-helical dihydropyridine receptor segment". Biochemical Journal 370, nr 2 (1.03.2003): 517–27. http://dx.doi.org/10.1042/bj20021488.

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An α-helical II—III loop segment of the dihydropyridine receptor activates the ryanodine receptor calcium-release channel. We describe a novel manipulation in which this agonist's activity is increased by modifying its surface structure to resemble that of a toxin molecule. In a unique system, native β-sheet scorpion toxins have been reported to activate skeletal muscle ryanodine receptor calcium channels with high affinity by binding to the same site as the lower-affinity α-helical dihydropyridine receptor segment. We increased the alignment of basic residues in the α-helical peptide to mimic the spatial orientation of active residues in the scorpion toxin, with a consequent 2—20-fold increase in the activity of the α-helical peptide. We hypothesized that, like the native peptide, the modified peptide and the scorpion toxin may bind to a common site. This was supported by (i) similar changes in ryanodine receptor channel gating induced by the native or modified α-helical peptide and the β-sheet toxin, a 10—100-fold reduction in channel closed time, with a ≤2-fold increase in open dwell time and (ii) a failure of the toxin to further activate channels activated by the peptides. These results suggest that diverse structural scaffolds can present similar conformational surface properties to target common receptor sites.

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Mitpuangchon, Natrada, Kwan Nualcharoen, Singtoe Boonrotpong i Patamarerk Engsontia. "Identification of Novel Toxin Genes from the Stinging Nettle Caterpillar Parasa lepida (Cramer, 1799): Insights into the Evolution of Lepidoptera Toxins". Insects 12, nr 5 (29.04.2021): 396. http://dx.doi.org/10.3390/insects12050396.

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Many animal species can produce venom for defense, predation, and competition. The venom usually contains diverse peptide and protein toxins, including neurotoxins, proteolytic enzymes, protease inhibitors, and allergens. Some drugs for cancer, neurological disorders, and analgesics were developed based on animal toxin structures and functions. Several caterpillar species possess venoms that cause varying effects on humans both locally and systemically. However, toxins from only a few species have been investigated, limiting the full understanding of the Lepidoptera toxin diversity and evolution. We used the RNA-seq technique to identify toxin genes from the stinging nettle caterpillar, Parasa lepida (Cramer, 1799). We constructed a transcriptome from caterpillar urticating hairs and reported 34,968 unique transcripts. Using our toxin gene annotation pipeline, we identified 168 candidate toxin genes, including protease inhibitors, proteolytic enzymes, and allergens. The 21 P. lepida novel Knottin-like peptides, which do not show sequence similarity to any known peptide, have predicted 3D structures similar to tarantula, scorpion, and cone snail neurotoxins. We highlighted the importance of convergent evolution in the Lepidoptera toxin evolution and the possible mechanisms. This study opens a new path to understanding the hidden diversity of Lepidoptera toxins, which could be a fruitful source for developing new drugs.

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Van Baelen, Anne-Cécile, Xavier Iturrioz, Marion Chaigneau, Pascal Kessler, Catherine Llorens-Cortes, Denis Servent, Nicolas Gilles i Philippe Robin. "Characterization of the First Animal Toxin Acting as an Antagonist on AT1 Receptor". International Journal of Molecular Sciences 24, nr 3 (24.01.2023): 2330. http://dx.doi.org/10.3390/ijms24032330.

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The renin-angiotensin system (RAS) is one of the main regulatory systems of cardiovascular homeostasis. It is mainly composed of angiotensin-converting enzyme (ACE) and angiotensin II receptors AT1 and AT2. ACE and AT1 are targets of choice for the treatment of hypertension, whereas the AT2 receptor is still not exploited due to the lack of knowledge of its physiological properties. Peptide toxins from venoms display multiple biological functions associated with varied chemical and structural properties. If Brazilian viper toxins have been described to inhibit ACE, no animal toxin is known to act on AT1/AT2 receptors. We screened a library of toxins on angiotensin II receptors with a radioligand competition binding assay. Functional characterization of the selected toxin was conducted by measuring second messenger production, G-protein activation and β-arrestin 2 recruitment using bioluminescence resonance energy transfer (BRET) based biosensors. We identified one original toxin, A-CTX-cMila, which is a 7-residues cyclic peptide from Conus miliaris with no homology sequence with known angiotensin peptides nor identified toxins, displaying a 100-fold selectivity for AT1 over AT2. This toxin shows a competitive antagonism mode of action on AT1, blocking Gαq, Gαi3, GαoA, β-arrestin 2 pathways and ERK1/2 activation. These results describe the first animal toxin active on angiotensin II receptors.

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Rozprawy doktorskie na temat "Peptide toxin"

Thompson, Christopher Hal. "Identification and characterization of a peptide toxin inhibitor of ClC-2 chloride channels". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26604.

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Thesis (Ph.D)--Biology, Georgia Institute of Technology, 2009.
Committee Chair: McCarty, Nael; Committee Co-Chair: Harvey, Stephen; Committee Member: Hartzell, Criss; Committee Member: Kubanek, Julia; Committee Member: Lee, Robert. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Ekberg, Jenny. "Novel peptide toxin and protein modulators of voltage-gated ion channels /". [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe20102.pdf.

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Droctove, Laura. "Premières toxines Kunitz antagonistes du récepteur de type 2 à la vasopressine : étude pharmacodynamique et relations structure-activité". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS009/document.

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La mambaquarétine-1 (MQ-1), une toxine du mamba vert, est le tout premier peptide Kunitz à bloquer sélectivement l’activité du récepteur de type 2 à la vasopressine (V2R). Celui-ci contrôle la concentration finale des urines dans le rein. Impliqué dans plusieurs pathologies, son inhibition est actuellement considérée comme la meilleure stratégie thérapeutique dans le traitement de la polykystose rénale, une maladie génétique héréditaire. L’étude pharmacodynamique de MQ-1 sur des rats sains a confirmé son activité in vivo qui se traduit par un effet aquarétique dépendant de la dose. L’effet maximum est atteint 2 heures après injection intrapéritonéale et disparait avec un temps de demi-vie biologique variant de 1 à 4 heures selon la dose. L’administration quotidienne d’une faible dose a montré une accumulation de l’effet les trois premiers jours, avant un plateau, suggérant une activité résiduelle au-delà de 24 heures. Le criblage des trois autres venins de mambas ainsi qu’une analyse comparée des séquences peptidiques les plus proches dans les bases de données ont révélé l’existence d’un groupe phylogénétique de onze toxines Kunitz antagonistes de V2R. Une approche innovante, combinant tests de liaison de variants de MQ-1 et modélisation du complexe MQ-1-V2R, a permis de décrypter une partie du pharmacophore de la toxine. Les deux partenaires partagent une importante complémentarité ionique impliquant plusieurs boucles extracellulaires du récepteur, et une région hydrophobe de MQ-1 interagit au cœur de V2R à proximité de son site orthostérique supposé. Enfin, une première collaboration avec une industrie pharmaceutique a mis en évidence les points critiques à approfondir pour aboutir au développement thérapeutique de MQ-1
Mambaquaretin-1 (MQ-1), a green mamba toxin, is the very first Kunitz peptide to selectively hinder the vasopressin type 2 receptor (V2R) activation. This receptor controls the final concentration of urine in kidneys. Involved in a number of pathologies, its inhibition is currently considered as the best therapeutic strategy in the treatment of polycystic kidney disease, a hereditary genetic disease. Pharmacodynamic study of MQ-1 carried out on healthy rats confirmed its in vivo activity which consists in inducing a dose-dependent aquaretic effect. Maximum effect is reached 2 hours after an intraperitoneal injection and disappears in a biological half-life ranging from 1 to 4 hours according to the dose. The daily injection of small quantities pointed to a cumulative effect over the first three days, leading to a plateau, which suggests a residual activity exceeding 24 hours. The screening of the three other mamba venoms along with a comparative analysis of the closest peptide sequences reported in databases revealed the existence of a phylogenetic group of eleven V2R antagonist Kunitz toxins. An innovative approach combining binding assays on MQ-1 variants and the modelling of the MQ-1-V2R complex has led to a partial deciphering of the pharmacophore of the toxin. The two partners share a significant ionic complementarity involving a number of extracellular loops of the receptor, and a hydrophobic region of MQ-1 interacts within V2R in the vicinity of its supposed orthosteric site. Lastly, a collaboration initiated with a pharmaceutical company brought out the need for the closer scrutiny of some crucial points to succeed in a therapeutic development of MQ-1

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Blagojevic, Mariana. "Epithelial cell death induced by Candidalysin, a cytolytic peptide toxin of Candida albicans". Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/epithelial-cell-death-induced-by-candidalysin-a-cytolytic-peptide-toxin-of-candida-albicans(7a2a83b3-dd43-472f-87b3-1d157687b440).html.

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Microbial infections contribute significantly to morbidity and mortality in humans. Fungi are often an under-represented component of the microbial communities that colonise mucosal surfaces. The most common human fungal pathogens are the Candida species, of which Candida albicans is the most prevalent. C. albicans has an asymptomatic carriage rate of approximately 60% in the human population, where it resides as a member of the microflora that colonises the mucosal surfaces of the body. C. albicans is a polymorphic fungus capable of growing in a number of distinct morphological forms. At mucosal surfaces, growth of C. albicans in the unicellular yeast form is typically associated with commensalism, whereas the production of filamentous hyphae is associated with fungal overgrowth and pathogenesis. In healthy individuals, the immune system functions to restrict the growth of C. albicans hyphae, preventing infection. However, in the absence of effective immune surveillance, C. albicans hyphae can invade the mucosal surfaces of the body, causing infection and tissue damage. Translocation of C. albicans across mucosal barriers and invasion of underlying tissues is a major risk-factor for the development of life-threatening systemic infection in immune-compromised individuals. The hyphae of C. albicans secrete Candidalysin, a toxin essential for epithelial damage and activation of mucosal immune responses. Cellular damage sustained during infection can often result in cell death by apoptosis, necrosis, necroptosis or pyroptosis. While cell death is often regarded as being beneficial for microbial pathogenesis, it is becoming increasingly clear that cell death can also influence host defence by initiating specific immune responses that contribute to microbial clearance. Collectively, these data demonstrate that oral epithelial cells respond to the secreted fungal toxin Candidalysin by triggering numerous cellular stress responses that are intimately linked with the induction of cellular death. Candidalysin was observed to induce necrosis, but not apoptosis, necroptosis or pyroptosis, and promoted inflammatory responses through a mechanism involving necrosis-dependent release of pro-IL-1β and pro-IL-18.

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Johnson, Stephen Roy. "A Biochemical And Pharmacological Characterization Of A Novel Neuroactive Peptide From The Neotropical Hunting Ant Dinoponera Australis". Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1879010761&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Thesis (Ph. D.)--Southern Illinois University Carbondale, 2009.
"Department of Pharmacology." Keywords: Peptides, Toxins, Venom, Neuroactive peptide, Neurotoxins. Includes bibliographical references (p. 200-210). Also available online.

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Perez, Morales Tiara G. "Production of and Response to the Cannibalism Peptide SDP in Bacillus subtilis". Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4895.

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The Gram positive soil dwelling bacteria Bacillus subtilis produces spores when encountered with a low nutrient environment. However, B. subtilis can delay spore production by a mechanism known as cannibalism. Cannibalism is a process by which B. subtilis delays commitment to sporulation by killing a subpopulation of its cells. This process involves production of two toxins, SDP and SKF. SDP is a 42 amino acid peptide with a disulfide bond derived from the internal cleavage of its precursor protein pro-SdpC. pro-SdpC is part of the sdpABC operon. Production of extracellular SDP induces expression of the sdpRI operon. Encoded in this operon is the negative regulator SdpR and SdpI. SdpI is a dual function protein which acts both as a signal transduction protein and the immunity factor against SDP. The current model states that production of SDP is sensed via SdpI. SdpI will sequester SdpR to the membrane in response and allow for sdpRI expression. The aims of this dissertation are to establish the requirements for SDP production and its response via SdpI/SdpR during cannibalism. Studies in Chapter II were carried out to determine the factors required for production of the antimicrobial peptide SDP. Site directed mutagenesis of the leader signal peptide sequence in pro-SdpC demonstrated that proper signal peptide cleavage was required for SDP production. Additional site directed mutants of the cysteine residues in pro-SdpC revealed that these are not required for SDP toxic activity. These studies also included deletions within the sdpABC operon and revealed that the two proteins of unknown function, SdpA and SdpB are required for SDP production. Using mass spectrometry analysis, we found that SdpA and SdpB together are required to produce the active 42 amino acid peptide SDP. Taken together we concluded that SDP production was a multi step process which required proteins encoded within the operon and additional processing supplemented in the cell. In Chapter III we investigated the role of SdpI, specifically what residues were required for the signaling and immunity functions observed. Our initial screen, included site directed mutagenesis of highly conserved residues between the 4th and 5th transmembrane domains of SdpI. These resulted in over 20 SdpI mutants generated. From these, only two SdpI mutants had defects in either signal transduction or SDP immunity. Additional localized mutagenesis was used to isolate two other mutants in SdpI which only affected signal transduction or SDP immunity. SdpI signaling-immunity+ mutants presented a defect in SdpR membrane sequestration and sdpRIinduction. Our findings suggest these types of SdpI mutants may be important for the downstream effect of SdpR membrane sequestration. SdpI signaling+ immunity- mutants revealed defects in SDP protection. Some of the residues mutated were conserved in other SdpI homologs. Site directed mutagenesis of these conserved residues in the SdpI ortholog YfhL showed these are also required for SDP resistance. For the first time, we were able to identify mutations which affected only SDP immunity and gained further insight into how SdpI signaling-immunity+ mutants play a role during signal transduction. In Chapter IV we initiated studies to define what regions of the negative regulator SdpR are important for its function during cannibalism. We employed localized mutagenesis to identify SdpR mutants which decreased sdpRIexpression even in the presence of inducing signal. We isolated three such SdpR mutants, referred to as super repressors. We expect these SdpR super repressors are unable to be sequestered to the membrane in the presence of SDP.

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Voegele, Alexis. "Study of the translocation mechanism of the cyaa toxin from bordetella pertussis". Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/VOEGELE_Alexis_va.pdf.

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La toxine adénylcyclase (CyaA) est un des principaux facteurs de virulence produite par Bordetella pertussis, l’agent de la coqueluche. CyaA a l’unique capacité de transloquer son domaine catalytique directement à travers la membrane plasmique. Puis le domaine catalytique lie la calmoduline (CaM) pour produire de grandes quantités d’AMPc, conduisant à l’intoxication de la cellule. Bien que plusieurs modèles aient été proposés, le mécanisme moléculaire et les forces impliquées dans la translocation de CyaA restent peu connus. Un gradient de calcium, un potentiel de membrane et des acylations post-traductionnelles sont requis pour la translocation de CyaA. Pendant mon doctorat, je me suis principalement intéressé au processus de translocation. Il a été montré précédemment que la suppression de la région de translocation abolit le passage du domaine catalytique. Dans cette région, le peptide P454 (résidus 454 à 484 de CyaA) a été identifié et montre des propriétés membranaires, i.e interaction avec la membrane, repliement en hélice α au contact de la membrane et perméabilisation membranaire. Nous avons étudié le rôle de P454 dans le processus de translocation. Nous avons observé que des lipides fluides et chargés négativement favorisent l’insertion de P454 dans les membranes. Le peptide possède deux arginines qui sont impliquées dans ses activités membranaires. P454 possède aussi la capacité de transloquer à travers la membrane et de former un complexe avec la CaM. Nous avons identifié plusieurs résidus de P454 impliqués dans la liaison à la membrane et la CaM. Dans le contexte de la toxine entière, ces résidus sont essentiels pour la translocation du domaine catalytique et la production d’AMPc. On propose un modèle de translocation dans lequel le segment P454 de la région de translocation déstabilise la membrane, favorisant sa translocation. Dans le cytosol, le segment P454 est piégé par la CaM et le complexe pourrait agir comme une force tirant le domaine catalytique à travers la membrane. Nous avons aussi montré que la liaison à la CaM du peptide liant la CaM dans le domaine catalytique induit des effets allostériques qui stabilisent le site catalytique, permettant la catalyse rapide d’ATP en AMPc. La pertinence de ces résultats pour la translocation et l’activation de CyaA sont discutées
The adenylate cyclase toxin (CyaA) is one of the major virulence factor produced by Bordetella pertussis, the causative agent of whopping cough. CyaA has the unique capacity to translocate its catalytic domain directly across the plasma membrane. Then, the catalytic domain binds to calmodulin (CaM) to produce high levels of cAMP, leading to cell intoxication. Although several models have been proposed, the molecular mechanism and the forces involved in the translocation of CyaA remain elusive. The calcium gradient, the membrane potential across the plasma membrane and post-translational acylation are required for an efficient CyaA translocation. During my PhD, I mainly investigated the translocation process. It has been previously shown that deletion of the translocation region abolishes the delivery of the catalytic domain into the cytosol of target cells. In this region, the peptide P454 (residues 454 to 484 of CyaA) was identified and exhibits membrane-active properties related to antimicrobial peptides, i.e membrane interaction, α-helical folding upon membrane insertion and membrane permeabilization. We have investigated the role of P454 on the translocation process. We observed that negatively charged and fluidic membrane favor P454 membrane insertion. The peptide contains two arginine residues that are critically involved in its membrane-active properties. We further identified that P454 exhibits the intrinsic propensity to translocate across lipid bilayers and forms a stable complex with CaM. We identified several residues from P454 involved in both membrane interaction and CaM binding. We showed in the context of the full-length CyaA toxin that these residues are essential for the efficient translocation of the catalytic domain into the cell and production of cAMP. We propose a translocation model in which the membrane-active P454 segment from the translocation region destabilizes the membrane, favoring its translocation. In the cytosol, the P454 segment is trapped by CaM and the formation of the complex may act as a driving force pulling the catalytic domain across the plasma membrane. We further showed that CaM binding to the main CaM-binding site in the catalytic domain induces local and long-range allosteric effects that stabilize the enzymatic site, allowing fast ATP catalysis to cAMP, leading to host subversion. The relevance of these results for the translocation and activation of CyaA are discussed

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Wernecke, Julia [Verfasser]. "Biophysical characterisation of the fungal peptide toxin Ece1-III and its interaction with lipid membranes / Julia Wernecke". Lübeck : Zentrale Hochschulbibliothek Lübeck, 2016. http://d-nb.info/1121535852/34.

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Tisseyre, Céline. "La maurocalcine : substance naturelle d'intérêt thérapeutique". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENV047/document.

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La maurocalcine (MCa) est une toxine de 33 acides aminés initialement issue du venin du scorpionScorpio maurus palmatus, et est considérée comme faisant partie de la famille des CPP(Cell Penetrating Peptides) depuis de nombreuses années déjà. La MCa présente donc un intérêtthérapeutique certain dans le domaine de la délivrance intracellulaire de cargos, et lestravaux exposés ici cherchent à caractériser au mieux les propriétés de pénétration de la moléculenative ainsi que celle de certains de ses variants.Après avoir quantifié l’internalisation de plusieurs variants tronqués (linéaires), j’ai pu mettreen évidence le fait que tous ces analogues testés ont une capacité à être internalisés bien plusélevée que celle des CPP de référence (notamment Tat et la pénétratine). Parmi ces variants,l’analogue MCaUF1−9 présente l’avantage d’un temps de rétention relativement élevé au seindes cellules, ainsi que d’une accumulation légèrement accrue en environnement acide (ce quiadvient lors de la formation tumeurs solides). Ce nouveau CPP possède donc un certain potentielthérapeutique mais l’étude de la MCa native, remarquablement stable in vivo, reste plusque jamais d’actualité
Maurocalcine (MCa) is a 33-mer toxin originally isolated from the venom of the scorpioScorpio maurus palmatus, and has been considered as a cell-penetrating peptide (CPP) for severalyears. MCa presents a therapeutic interest for the intracellular delivery of cargoes, andthis thesis aims to characterise the cell penetration properties of the native molecule as well assome of its variants’.After quantifying several truncated (linear) variants’ internalisation, I have been able tohighlight the fact that all of those analogs possess a higher internalization ability than those ofstandard CPP (especially Tat and penetratin). Among those variants, the analog MCaUF1−9 hasa relatively high rentention time within cells, as well as a slightly increased accumulation whenin an acidic environment (which occurs during solid tumours formation). This new CPP showsa certain therapeutic potential but the study of nativeMCa, remarkably stable in vivo, remainsa priority

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Höfs, Sarah [Verfasser], Bernhard Gutachter] Hube, Joachim [Gutachter] Ernst i Kerstin [Gutachter] [Voigt. "Identification of Candidalysin : a Candida albicans peptide toxin involved in epithelial damage / Sarah Höfs ; Gutachter: Bernhard Hube, Joachim Ernst, Kerstin Voigt". Jena : Friedrich-Schiller-Universität Jena, 2016. http://d-nb.info/1177608758/34.

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Książki na temat "Peptide toxin"

Binnington-Boyd, Beth A. Studies to determine the vaccine potential of the B-subunit of Shiga-like toxin 1 and its peptide fragments. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1992.

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F, Watanabe Mariyo, red. Toxic microcystis. Boca Raton, FL: CRC Press, 1996.

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International Agency for Research on Cancer i World Health Organization, red. Ingested nitrate and nitrite, and cyanobacterial peptide toxins. Lyon, France: International Agency for Research on Cancer, 2010.

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Gianfranco, Menestrina, i Dalla Serra Mauro, red. Pore-forming peptides and protein toxins. London: Taylor and Francis, 2003.

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Meriluoto, Jussi. Liquid chromatographic analysis of cyanobacterial peptide hepatotoxins. Åbo: Åbo Akademis förlag, 1990.

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Walton, Jonathan. The Cyclic Peptide Toxins of Amanita and Other Poisonous Mushrooms. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-76822-9.

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Stocklin, Reto. A Handbook of Animal Toxins: Peptides and Proteins. John Wiley & Sons, 2004.

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Menestrina, Gianfranco, i M. Dalla Sera. Pore-Forming Peptides and Protein Toxins. Taylor & Francis Group, 2003.

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Menestrina, Gianfranco, i M. Dalla Sera. Pore-Forming Peptides and Protein Toxins. Taylor & Francis Group, 2003.

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Menestrina, Gianfranco, i M. Dalla Sera. Pore-Forming Peptides and Protein Toxins. Taylor & Francis Group, 2003.

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Części książek na temat "Peptide toxin"

Norton, Raymond S. "Peptide Toxin Structure and Function by NMR". W Modern Magnetic Resonance, 1–18. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-28275-6_120-1.

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Norton, Raymond S. "Peptide Toxin Structure and Function by NMR". W Modern Magnetic Resonance, 2081–97. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-28388-3_120.

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McDonough, Stefan I. "Peptide Toxin Inhibition of Voltage Gated Calcium Channels". W Calcium Channel Pharmacology, 95–142. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/978-1-4419-9254-3_4.

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Murphy, John R., Diane P. Williams, Tetsuyuki Kiyokawa, Paige L. Anderson i Terry B. Strom. "Diphtheria Toxin-Related Peptide Hormone Fusion Proteins: New Toxins with Therapeutic Potential". W Cytotoxic Anticancer Drugs: Models and Concepts for Drug Discovery and Development, 281–301. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3492-1_17.

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Lee, Sejeong, Nessim Kichik, Olivia W. Hepworth, Jonathan P. Richardson i Julian R. Naglik. "In Vitro Biophysical Characterization of Candidalysin: A Fungal Peptide Toxin". W Methods in Molecular Biology, 163–76. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2549-1_12.

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Banerjee, Aishiki, i Saurav Saha. "Antimicrobial Peptide and Toxin-Based Mutualism: Obligate Symbiotic Entomopathogenic Nematode—Bacterium Associations". W Microbes in Microbial Communities, 91–114. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-5617-0_4.

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Russell, Michael W., Hong-Yin Wu, Pamela L. White, Ichiro Takahashi, Nobuo Okahashi i Toshihiko Koga. "Peroral Immunization with a Cholera Toxin-Linked Bacterial Protein Antigen and Synthetic Peptide". W Genetically Engineered Vaccines, 199–207. Boston, MA: Springer US, 1992. http://dx.doi.org/10.1007/978-1-4615-3410-5_22.

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Lee, Jane, Phil Kennedy i Jacob M. Waugh. "Experiences with CPP-Based Self Assembling Peptide Systems for Topical Delivery of Botulinum Toxin". W Methods in Molecular Biology, 397–415. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-2806-4_27.

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Murphy, John R. "Diphtheria-related peptide hormone gene fusions: A molecular genetic approach to chimeric toxin development". W Immunotoxins, 123–40. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-1083-9_9.

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Suryanarayana, Nagendra, Vanlalhmuaka, Kulanthaivel Thavachelvam i Urmil Tuteja. "Humoral Responses of In Silico Designed Immunodominant Antigenic Peptide Cocktails from Anthrax Lethal Toxin Components". W Recent advances in Applied Microbiology, 249–58. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-5275-0_12.

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Streszczenia konferencji na temat "Peptide toxin"

Bozsó, Zsolt, Ferenc Bogár, János Szolomájer, Zoltán Kele, Ágota Csóti, Tibor G. Szántó, György Panyi i Gábor K. Tóth. "Design and Synthesis of Selective Ion Channel Blocker Peptide Toxin Analogs". W 36th European Peptide Symposium. The European Peptide Society, 2022. http://dx.doi.org/10.17952/36eps/36eps.2022.093.

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Bozsó, Zsolt, Ferenc Bogár, Janos Szolomájer, Zoltán Kele, Ágota Csóti, Tibor G. Szántó, György Panyi i Gábor K. Tóth. "Design and Synthesis of Selective Ion Channel Blocker Peptide Toxin Analogs". W 36th European Peptide Symposium. The European Peptide Society, 2022. http://dx.doi.org/10.17952/36eps.2022.093.

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Iglesias-García, Lucía C., Jesica A. Rodríguez, Gabriela R. Barredo-Vacchelli, Juan M. Minoia, Silvia A. Camperi, Gerardo Acosta i Fernando Albericio. "Identification and Synthesis of Epitopes from a Phoneutria Nigriventer Toxin to Produce Immunogens". W 36th European Peptide Symposium. The European Peptide Society, 2022. http://dx.doi.org/10.17952/36eps.2022.045.

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Iglesias-García, Lucía C., Jésica A. Rodríguez, Gabriela R. Barredo-Vacchelli, Juan M. Minoia, Gerardo Acosta, Fernando Albericio i Silvia A. Camperi. "Identification and Synthesis of Epitopes from a Phoneutria Nigriventer Toxin to Produce Immunogens". W 36th European Peptide Symposium. The European Peptide Society, 2022. http://dx.doi.org/10.17952/36eps/36eps.2022.045.

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Estrada, Rosendo, Redwan Huq, Rajeev Tajhya, Satendra Chauhan, Christine Beeton i Michael W. Pennington. "Kv1.3 Selective Peptides Based Upon N-Terminal Extension and Internal Substitutions of ShK Toxin". W The 24th American Peptide Symposium. Prompt Scientific Publishing, 2015. http://dx.doi.org/10.17952/24aps.2015.238.

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Ojha, Sumedha, Kanika Kundu i Subir Kundu. "Antimicrobial peptide Microcin C7 as an alternative drug candidate against Diphtheria toxin". W 2016 International Conference on Bioinformatics and Systems Biology (BSB). IEEE, 2016. http://dx.doi.org/10.1109/bsb.2016.7552140.

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Mikheeva, N. A., E. P. Drozhdina i N. A. Kurnosova. "Morphofunctional features of proliferating cells exposed to PSMA peptide". W VIII Vserossijskaja konferencija s mezhdunarodnym uchastiem «Mediko-fiziologicheskie problemy jekologii cheloveka». Publishing center of Ulyanovsk State University, 2021. http://dx.doi.org/10.34014/mpphe.2021-142-144.

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The effect of the synthetic PSMA peptide on dividing cells of laboratory animals was studied. The experiment was carried out on male white laboratory mice of the BALB/c-line. The toxic effect of PSMA peptidi was evaluated at therapeutic (1.4 μg / kg of animal weight or 0.04 μg / animal) and subtoxic (140 μg / kg of animal weight or 4.0 μg / animal) doses. The cytotoxic effect of PSMA peptide on red bone marrow cells and cambial intestinal cells of the of laboratory mice was determined. A decrease in the proliferative activity of the colon crypt cells was revealed upon administration of a subtoxic dose of the PSMA peptide and there were no signs of toxic damage to the red bone marrow cells of animals. Key words: toxicity, proliferation, synthetic peptides, mitotic index, micronucleus test.

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Rigby, Mike, Paul Beswick, Gemma Mudd, Katerine Van Rietschoten, Liuhong Chen, Sophie M. Watcham, Heather Allen i in. "Abstract 4479: BT8009: A bicyclic peptide toxin conjugate targeting Nectin-4 (PVRL4) displays efficacy in preclinical tumor models". W Proceedings: AACR Annual Meeting 2019; March 29-April 3, 2019; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-4479.

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Sarigiannis, Yiannis, Constantinos Avraamides, Spiridoula Diavoli, Ariana Robertson, Manos Vlasiou, Elena Mourelatou i Christos Petrou. "Linear Scorpion Peptides: An unexplored pool for peptide hydrogels". W 1st International Electronic Conference on Toxins. Basel, Switzerland: MDPI, 2021. http://dx.doi.org/10.3390/iect2021-09124.

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Raporty organizacyjne na temat "Peptide toxin"

Gurevitz, Michael, Michael E. Adams, Boaz Shaanan, Oren Froy, Dalia Gordon, Daewoo Lee i Yong Zhao. Interacting Domains of Anti-Insect Scorpion Toxins and their Sodium Channel Binding Sites: Structure, Cooperative Interactions with Agrochemicals, and Application. United States Department of Agriculture, grudzień 2001. http://dx.doi.org/10.32747/2001.7585190.bard.

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Integrated pest management in modern crop protection may combine chemical and biological insecticides, particularly due to the risks to the environment and livestock arising from the massive use of non-selective chemicals. Thus, there is a need for safer alternatives, which target insects more specifically. Scorpions produce anti-insect selective polypeptide toxins that are biodegradable and non-toxic to warm-blooded animals. Therefore, integration of these substances into insect pest control strategies is of major importance. Moreover, clarification of the molecular basis of this selectivity may provide valuable information pertinent to their receptor sites and to the future design of peptidomimetic anti-insect specific substances. These toxins may also be important for reducing the current overuse of chemical insecticides if they produce a synergistic effect with conventional pesticides. Based on these considerations, our major objectives were: 1) To elucidate the three-dimensional structure and toxic-site of scorpion excitatory, "depressant, and anti-insect alpha toxins. 2) To obtain an initial view to the sodium channel recognition sites of the above toxins by generating peptide decoys through a phage display system. 3) To investigate the synergism between toxins and chemical insecticides. Our approach was to develop a suitable expression system for toxin production in a recombinant form and for elucidation of toxin bioactive sites via mutagenesis. In parallel, the mode of action and synergistic effects of scorpion insecticidal toxins with pyrethroids were studied at the sodium channel level using electrophysiological methods. Objective 1 was achieved for the alpha toxin, LqhaIT Zilberberg et al., 1996, 1997; Tugarinov et al., 1997; Froy et al., 2002), and the excitatory toxin, Bj-xtrIT (Oren et al., 1998; Froy et al., 1999; unpublished data). The bioactive surface of the depressant toxin, LqhIT2, has been clarified and a crystal of the toxin is now being analyzed (unpublished). Objective 2 was not successful thus far as no phages that recognize the toxins were obtained. We therefore initiated recently an alternative approach, which is introduction of mutations into recombinant channels and creation of channel chimeras. Objective 3 was undertaken at Riverside and the results demonstrated synergism between LqhaIT or AaIT and pyrethroids (Lee et al., 2002). Furthermore, negative cross-resistance between pyrethroids and scorpion toxins (LqhaIT and AaIT) was demonstrated at the molecular level. Although our study did not yield a product, it paves the way for future design of selective pesticides by capitalizing on the natural competence of scorpion toxins to distinguish between sodium channels of insects and vertebrates. We also show that future application of anti-insect toxins may enable to decrease the amounts of chemical pesticides due to their synergism.

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Gurevitz, Michael, William A. Catterall i Dalia Gordon. face of interaction of anti-insect selective toxins with receptor site-3 on voltage-gated sodium channels as a platform for design of novel selective insecticides. United States Department of Agriculture, grudzień 2013. http://dx.doi.org/10.32747/2013.7699857.bard.

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Voltage-gated sodium channels (Navs) play a pivotal role in excitability and are a prime target of insecticides like pyrethroids. Yet, these insecticides are non-specific due to conservation of Navs in animals, raising risks to the environment and humans. Moreover, insecticide overuse leads to resistance buildup among insect pests, which increases misuse and risks. This sad reality demands novel, more selective, insect killers whose alternative use would avoid or reduce this pressure. As highly selective insect toxins exist in venomous animals, why not exploit this gift of nature and harness them in insect pest control? Many of these peptide toxins target Navs, and since their direct use via transformed crop plants or mediator microorganisms is problematic in public opinion, we focus on the elucidation of their receptor binding sites with the incentive of raising knowledge for design of toxin peptide mimetics. This approach is preferred nowadays by agro-industries in terms of future production expenses and public concern. However, characterization of a non-continuous epitope, that is the channel receptor binding site for such toxins, requires a suitable experimental system. We have established such a system within more than a decade and reached the stage where we employ a number of different insect-selective toxins for the identification of their receptor sites on Navs. Among these toxins we wish to focus on those that bind at receptor site-3 and inhibit Nav inactivation because: (1) We established efficient experimental systems for production and manipulation of site-3 toxins from scorpions and sea anemones. These peptides vary in size and structure but compete for site-3 on insect Navs. Moreover, these toxins exhibit synergism with pyrethroids and with other channel ligands; (2) We determined their bioactive surfaces towards insect and mammalian receptors (see list of publications); (3) We found that despite the similar mode of action on channel inactivation, the preference of the toxins for insect and mammalian channel subtypes varies greatly, which can direct us to structural features in the basis of selectivity; (4) We have identified by channel loop swapping and point mutagenesis extracellular segments of the Navinvolved with receptor site-3. On this basis and using channel scanning mutagenesis, neurotoxin binding, electrophysiological analyses, and structural data we offer: (i) To identify the residues that form receptor site-3 at insect and mammalian Navs; (ii) To identify by comparative analysis differences at site-3 that dictate selectivity toward various Navs; (iii) To exploit the known toxin structures and bioactive surfaces for modeling their docking at the insect and mammalian channel receptors. The results of this study will enable rational design of novel anti-insect peptide mimetics with minimized risks to human health and to the environment. We anticipate that the release of receptor site-3 molecular details would initiate a worldwide effort to design peptide mimetics for that site. This will establish new strategies in insect pest control using alternative insecticides and the combined use of compounds that interact allosterically leading to increased efficiency and reduced risks to humans or resistance buildup among insect pests.

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Camarero, J. Developing New Tools for the in vivo Generation/Screening of Cyclic Peptide Libraries. A New Combinatorial Approach for the Detection of Bacterial Toxin Inhibitors. Office of Scientific and Technical Information (OSTI), listopad 2006. http://dx.doi.org/10.2172/902307.

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Mevarech, Moshe, Jeremy Bruenn i Yigal Koltin. Virus Encoded Toxin of the Corn Smut Ustilago Maydis - Isolation of Receptors and Mapping Functional Domains. United States Department of Agriculture, wrzesień 1995. http://dx.doi.org/10.32747/1995.7613022.bard.

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Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. Resistance to the toxins is conferred by recessive nuclear genes. The toxins are encoded by genomic segments of resident double-strande RNA viruses. The best characterized toxin, KP6, is composed of two polypeptides, a and b, which are not covalently linked. It is encoded by P6M2 dsRNA, which has been cloned, sequenced and expressed in a variety of systems. In this study we have shown that the toxin acts on the membranes of sensitive cells and that both polypeptides are required for toxin activity. The toxin has been shown to function by creating new pores in the cell membrane and disrupting ion fluxes. The experiments performed on artificial phospholipid bilayers indicated that KP6 forms large voltage-independent, cation-selective channels. Experiments leading to the resolution of structure-function relationship of the toxin by in vitro analysis have been initiated. During the course of this research the collaboration also yielded X-ray diffracion data of the crystallized a polypeptide. The effect of the toxin on the pathogen has been shown to be receptor-mediated. A potential receptor protein, identified in membrane fractions of sensitive cells, was subjected to tryptic hydrolysis followed by amino-acid analysis. The peptides obtained were used to isolate a cDNA fragment by reverse PCR, which showed 30% sequence homology to the human HLA protein. Analysis of other toxins secreted by U. maydis, KP1 and KP4, have demonstrated that, unlike KP6, they are composed of a single polypeptide. Finally, KP6 has been expressed in transgenic tobacco plants, indicating that accurate processing by Kex2p-like activity occurs in plants as well. Using tobacco as a model system, we determined that active antifungal toxins can be synthesized and targeted to the outside of transgenic plant cells. If this methodology can be applied to other agronomically crop species, then U. maydis toxins may provide a novel means for biological control of pathogenic fungi.

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Shai, Yechiel, Arthur Aronson, Aviah Zilberstein i Baruch Sneh. Study of the Basis for Toxicity and Specificity of Bacillus thuringiensis d-Endotoxins. United States Department of Agriculture, styczeń 1996. http://dx.doi.org/10.32747/1996.7573995.bard.

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The report contains three parts which summarizes the three years achievements of the three participating research groups; The Weizmann group, Tel-Aviv group and Purdue group. The firs part describes the achievements obtained by Shai's group toward the elucidation of the mechanism of membrane insertion and the structural organization of the pores formed by the Cry3A and Cry1Ac B. thuringiensis d-endotoxins. For that purpose Shai's group synthesized, fluorescently labeled and structurally and functionally characterized peptides corresponding to the seven helices that compose the pore-forming domain of Cry3A toxin, including mutants peptides and the hairpin a4G-a5 of both Cry3A and Cry 1Ac toxins composed of a4, a5 and the loop connecting a4-a5. Among the synthesized peptides were three mutated a4 helices based on site directed mutagenesis done at Aronson's group that decreased or increased Cry 1Ac toxicity. The results of these studies are consistent with a situation in which only helices a4 anda5 insert into the membrane as a helical hairpin in an antiparallel manner, while the other helices lie on the membrane surface like ribs of an umbrella (the "umbrella model"). In order to test this model Shai's group synthesized the helical hairpin a4<-->a5 of both Cry3A and Cry 1 Ac toxins, as well. Initial functional and structural studies showed direct correlation between the properties of the mutated helices and the mutated Cry1Ac. Based on Shai's findings that a4 is the second helix besides a5 that insert into the membrane, Aronson and colleagues performed extensive mutation on this helix in the CrylAc toxin, as well as in the loop connecting helices 4 and 5, and helix 3 (part two of the report). In addition, Aronson performed studies on the effect of mutations or type of insect which influence the oligomerization either the Cry 1Ab or Cry 1Ac toxins with vesicles prepared from BBMV. In the third part of the report Zilberstein's and Sneh's groups describe their studies on the three domains of Cry 1C, Cry 1E and crylAc and their interaction with the epithelial membrane of the larval midgut. In these studies they cloned all three domains and combinations of two domains, as well as cloning of the pore forming domain alone and studying its interaction with BBMV. In addition they investigated binding of Cry1E toxin and Cry1E domains to BBMV prepared from resistant (R) or sensitive larvae. Finally they initiated expression of the loop a4G<-->a5 Cry3A in E. coli to be compared with the synthetic one done by Shai's group as a basis to develop a system to express all possible pairs for structural and functional studies by Shai's group (together with Y. Shai).

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Krishnamurthy, Thaiya. Investigation on Toxins and Venoms by Novel MS Techniques. Mass Spectral Investigations on Blue-Green Algal Toxic Peptides and Other Toxins. Fort Belvoir, VA: Defense Technical Information Center, sierpień 1990. http://dx.doi.org/10.21236/ada246914.

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Horwitz, Benjamin A., i Barbara Gillian Turgeon. Fungal Iron Acquisition, Oxidative Stress and Virulence in the Cochliobolus-maize Interaction. United States Department of Agriculture, marzec 2012. http://dx.doi.org/10.32747/2012.7709885.bard.

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Our project focused on genes for high affinity iron acquisition in Cochliobolus heterostrophus, a necrotrophic pathogen of maize, and their intertwined relationship to oxidative stress status and virulence of the fungus on the host. An intriguing question was why mutants lacking the nonribosomal peptide synthetase (NRPS) gene (NPS6) responsible for synthesis of the extracellular siderophore, coprogen, are sensitive to oxidative stress. Our overall objective was to understand the mechanistic connection between iron stress and oxidative stress as related to virulence of a plant pathogen to its host. The first objective was to examine the interface where small molecule peptide and reactive oxygen species (ROS) mechanisms overlap. The second objective was to determine if the molecular explanation for common function is common signal transduction pathways. These pathways, built around sensor kinases, response regulators, and transcription factors may link sequestering of iron, production of antioxidants, resistance to oxidative stress, and virulence. We tested these hypotheses by genetic manipulation of the pathogen, virulence assays on the host plant, and by following the expression of key fungal genes. An addition to the original program, made in the first year, was to develop, for fungi, a genetically encoded indicator of redox state based on the commercially available Gfp-based probe pHyper, designed for animal cell biology. We implemented several tools including a genetically encoded indicator of redox state, a procedure to grow iron-depleted plants, and constructed a number of new mutants in regulatory genes. Lack of the major Fe acquisition pathways results in an almost completely avirulent phenotype, showing how critical Fe acquisition is for the pathogen to cause disease. Mutants in conserved signaling pathways have normal ability to regulate NPS6 in response to Fe levels, as do mutants in Lae1 and Vel1, two master regulators of gene expression. Vel1 mutants are sensitive to oxidative stress, and the reason may be underexpression of a catalase gene. In nps6 mutants, CAT3 is also underexpressed, perhaps explaining the sensitivity to oxidative stress. We constructed a deletion mutant for the Fe sensor-regulator SreA and found that it is required for down regulation of NPS6 under Fe-replete conditions. Lack of SreA, though, did not make the fungus over-sensitive to ROS, though the mutant had a slow growth rate. This suggests that overproduction of siderophore under Fe-replete conditions is not very damaging. On the other hand, increasing Fe levels protected nps6 mutants from inhibition by ROS, implying that Fe-catalyzed Fenton reactions are not the main factor in its sensitivity to ROS. We have made some progress in understanding why siderophore mutants are sensitive to oxidative stress, and in doing so, defined some novel regulatory relationships. Catalase genes, which are not directly related to siderophore biosynthesis, are underexpressed in nps6 mutants, suggesting that the siderophore product (with or without bound Fe) may act as a signal. Siderophores, therefore, could be a target for intervention in the field, either by supplying an incorrect signal or blocking a signal normally provided during infection. We already know that nps6 mutants cause smaller lesions and have difficulty establishing invasive growth in the host. Lae1 and Vel1 are the first factors shown to regulate both super virulence conferred by T-toxin, and basic pathogenicity, due to unknown factors. The mutants are also altered in oxidative stress responses, key to success in the infection court, asexual and sexual development, essential for fungal dissemination in the field, aerial hyphal growth, and pigment biosynthesis, essential for survival in the field. Mutants in genes encoding NADPH oxidase (Nox) are compromised in development and virulence. Indeed the triple mutant, which should lack all Nox activity, was nearly avirulent. Again, gene expression experiments provided us with initial evidence that superoxide produced by the fungus may be most important as a signal. Blocking oxidant production by the pathogen may be a way to protect the plant host, in interactions with necrotrophs such as C. heterostrophus which seem to thrive in an oxidant environment.

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Sela, Shlomo, i Michael McClelland. Investigation of a new mechanism of desiccation-stress tolerance in Salmonella. United States Department of Agriculture, styczeń 2013. http://dx.doi.org/10.32747/2013.7598155.bard.

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Low-moisture foods (LMF) are increasingly involved in foodborne illness. While bacteria cannot grow in LMF due to the low water content, pathogens such as Salmonella can still survive in dry foods and pose health risks to consumer. We recently found that Salmonella secretes a proteinaceous compound during desiccation, which we identified as OsmY, an osmotic stress response protein of 177 amino acids. To elucidate the role of OsmY in conferring tolerance against desiccation and other stresses in Salmonella entericaserovarTyphimurium (STm), our specific objectives were: (1) Characterize the involvement of OsmY in desiccation tolerance; (2) Perform structure-function analysis of OsmY; (3) Study OsmY expression under various growth- and environmental conditions of relevance to agriculture; (4) Examine the involvement of OsmY in response to other stresses of relevance to agriculture; and (5) Elucidate regulatory pathways involved in controlling osmY expression. We demonstrated that an osmY-mutant strain is impaired in both desiccation tolerance (DT) and in long-term persistence during cold storage (LTP). Genetic complementation and addition of a recombinantOsmY (rOsmY) restored the mutant survival back to that of the wild type (wt). To analyze the function of specific domains we have generated a recombinantOsmY (rOsmY) protein. A dose-response DT study showed that rOsmY has the highest protection at a concentration of 0.5 nM. This effect was protein- specific as a comparable amount of bovine serum albumin, an unrelated protein, had a three-time lower protection level. Further characterization of OsmY revealed that the protein has a surfactant activity and is involved in swarming motility. OsmY was shown to facilitate biofilm formation during dehydration but not during bacterial growth under optimal growth conditions. This finding suggests that expression and secretion of OsmY under stress conditions was potentially associated with facilitating biofilm production. OsmY contains two conserved BON domains. To better understand the role of the BON sites in OsmY-mediated dehydration tolerance, we have generated two additional rOsmY constructs, lacking either BON1 or BON2 sites. BON1-minus (but not BON2) protein has decreased dehydration tolerance compared to intact rOsmY, suggesting that BON1 is required for maximal OsmY-mediated activity. Addition of BON1-peptide at concentration below 0.4 µM did not affect STm survival. Interestingly, a toxic effect of BON1 peptide was observed in concentration as low as 0.4 µM. Higher concentrations resulted in complete abrogation of the rOsmY effect, supporting the notion that BON-mediated interaction is essential for rOsmY activity. We performed extensive analysis of RNA expression of STm undergoing desiccation after exponential and stationary growth, identifying all categories of genes that are differentially expressed during this process. We also performed massively in-parallel screening of all genes in which mutation caused changes in fitness during drying, identifying over 400 such genes, which are now undergoing confirmation. As expected OsmY is one of these genes. In conclusion, this is the first study to identify that OsmY protein secreted during dehydration contributes to desiccation tolerance in Salmonella by facilitating dehydration- mediated biofilm formation. Expression of OsmY also enhances swarming motility, apparently through its surfactant activity. The BON1 domain is required for full OsmY activity, demonstrating a potential intervention to reduce pathogen survival in food processing. Expression and fitness screens have begun to elucidate the processes of desiccation, with the potential to uncover additional specific targets for efforts to mitigate pathogen survival in desiccation.

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Naim, Michael, Andrew Spielman, Shlomo Nir i Ann Noble. Bitter Taste Transduction: Cellular Pathways, Inhibition and Implications for Human Acceptance of Agricultural Food Products. United States Department of Agriculture, luty 2000. http://dx.doi.org/10.32747/2000.7695839.bard.

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Historically, the aversive response of humans and other mammals to bitter-taste substances has been useful for survival, since many toxic constituents taste bitter. Today, the range of foods available is more diverse. Many bitter foods are not only safe for consumption but contain bitter constituents that provide nutritional benefits. Despite this, these foods are often eliminated from our current diets because of their unacceptable bitterness. Extensive technology has been developed to remove or mask bitterness in foods, but a lack of understanding of the mechanisms of bitterness perception at the taste receptor level has prevented the development of inhibitors or efficient methods for reducing bitterness. In our original application we proposed to: (a) investigate the time course and effect of selected bitter tastants relevant to agricultural products on the formation of intracellular signal molecules (cAMP, IP3, Ca2+) in intact taste cells, in model cells and in membranes derived therefrom; (b) study the effect of specific bitter taste inhibitors on messenger formation and identify G-proteins that may be involved in tastant-induced bitter sensation; (c) investigate interactions and self-aggregation of bitter tastants within membranes; (d) study human sensory responses over time to these bitter-taste stimuli and inhibitors in order to validate the biochemical data. Quench-flow module (QFM) and fast pipetting system (FPS) allowed us to monitor fast release of the aforementioned signal molecules (cGMP, as a putative initial signal was substituted for Ca2+ ions) - using taste membranes and intact taste cells in a time range below 500 ms (real time of taste sensation) - in response to bitter-taste stimulation. Limonin (citrus) and catechin (wine) were found to reduce cellular cAMP and increase IP3 contents. Naringin (citrus) stimulated an IP3 increase whereas the cheese-derived bitter peptide cyclo(leu-Trp) reduced IP3 but significantly increased cAMP levels. Thus, specific transduction pathways were identified, the results support the notion of multiple transduction pathways for bitter taste and cross-talk between a few of those transduction pathways. Furthermore, amphipathic tastants permeate rapidly (within seconds) into liposomes and taste cells suggesting their availability for direct activation of signal transduction components by means of receptor-independent mechanisms within the time course of taste sensation. The activation of pigment movement and transduction pathways in frog melanophores by these tastants supports such mechanisms. Some bitter tastants, due to their amphipathic properties, permeated (or interacted with) into a bitter tastant inhibitor (specific phospholipid mixture) which apparently forms micelles. Thus, a mechanism via which this bitter taste inhibitor acts is proposed. Human sensory evaluation experiments humans performed according to their 6-n-propyl thiouracil (PROP) status (non-tasters, tasters, super-tasters), indicated differential perception of bitterness threshold and intensity of these bitter compounds by different individuals independent of PROP status. This suggests that natural products containing bitter compounds (e.g., naringin and limonin in citrus), are perceived very differently, and are in line with multiple transduction pathways suggested in the biochemical experiments. This project provides the first comprehensive effort to explore the molecular basis of bitter taste at the taste-cell level induced by economically important and agriculturally relevant food products. The findings, proposing a mechanism for bitter-taste inhibition by a bitter taste inhibitor (made up of food components) pave the way for the development of new, and perhaps more potent bitter-taste inhibitors which may eventually become economically relevant.

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