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Anthrax toxins 总被引:2,自引:0,他引:2
M. Mourez 《Reviews of Physiology, Biochemistry and Pharmacology》2004,152(1):135-164
Bacillus anthracis, the etiological agent of anthrax, secretes three polypeptides that assemble into toxic complexes on the cell surfaces of the host it infects. One of these polypeptides, protective antigen (PA), binds to the integrin-like domains of ubiquitously expressed membrane proteins of mammalian cells. PA is then cleaved by membrane endoproteases of the furin family. Cleaved PA molecules assemble into heptamers, which can then associate with the two other secreted polypeptides: edema factor (EF) and/or lethal factor (LF). The heptamers of PA are relocalized to lipid rafts where they are quickly endocytosed and routed to an acidic compartment. The low pH triggers a conformational change in the heptamers, resulting in the formation of cation-specific channels and the translocation of EF/LF. EF is a calcium- and calmodulin-dependent adenylate cyclase that dramatically raises the intracellular concentration of cyclic adenosine monophosphate (cAMP). LF is a zinc-dependent endoprotease that cleaves the amino terminus of mitogen-activated protein kinase kinases (Meks). Cleaved Meks cannot bind to their substrates and have reduced kinase activity, resulting in alterations of the signaling pathways they govern. The structures of PA, PA heptamer, EF, and LF have been solved and much is now known about the molecular details of the intoxication mechanism. The in vivo action of the toxins, on the other hand, is still poorly understood and hotly debated. A better understanding of the toxins will help in the design of much-needed anti-toxin drugs and the development of new toxin-based medical applications.Abbreviations CMG2 Capillary morphogenesis protein 2 - DTA Diphtheria toxin A chain - EF Edema factor - EFn N-terminal fragment of EF - ETx Edema toxin - GR Glucocorticoid receptors - GSK3 Glycogen synthase kinase 3 - I domain Integrin-like domain - iNOS Inducible nitric oxide synthase - LF Lethal factor - LFn N-terminal fragment of LF - LTx Lethal toxin - MAPK Mitogen-activated protein kinase - Mek MAPK kinases - PA Protective antigen - PA20 20-kDa N-terminal fragment of PA - PA63 63-kDa C-terminal fragment of PA - TEM8 Tumor endothelial marker 8 相似文献
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The ADP-ribosylating toxins (ADPRTs) are a family of toxins that catalyse the hydrolysis of NAD and the transfer of the ADP-ribose moiety onto a target. This family includes many notorious killers, responsible for thousands of deaths annually including: cholera, enterotoxic Escherichia coli, whooping cough, diphtheria and a plethora of Clostridial binary toxins. Despite their notoriety as pathogens, the ADPRTs have been extensively used as cellular tools to study and elucidate the functions of the small GTPases that they target. There are four classes of ADPRTs and at least one structure representative of each of these classes has been determined. They all share a common fold and several motifs around the active site that collectively facilitate the binding and transfer of the ADP-ribose moiety of NAD to their protein targets. In this review, we present an overview of the physiology and cellular qualities of the bacterial ADPRTs and take an in-depth look at the structural motifs that differentiate the different classes of bacterial ADPRTs in relation to their function. 相似文献
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The review of publications about protein toxins Y. pseudotuberculosis are presented. It includes the main data obtained by domestic and foreign investigators as well as the results of our own elaboration in the study of Y. pseudotuberculosis protein toxins. The guestions of isolation, purification, characterization of physico-chemical and biological properties, the mechanism action and role of toxins on pathogenesis of infection were discussed. 相似文献
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Schofield L 《Parasitology today (Personal ed.)》1997,13(7):275-6; author reply 276-7
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Mono‐glycosylation of host proteins is a common mechanism by which bacterial protein toxins manipulate cellular functions of eukaryotic target host cells. Prototypic for this group of glycosyltransferase toxins are Clostridium difficile toxins A and B, which modify guanine nucleotide‐binding proteins of the Rho family. However, toxin‐induced glycosylation is not restricted to the Clostridia. Various types of bacterial pathogens including Escherichia coli, Yersinia, Photorhabdus and Legionella species produce glycosyltransferase toxins. Recent studies discovered novel unexpected variations in host protein targets and amino acid acceptors of toxin‐catalysed glycosylation. These findings open new perspectives in toxin as well as in carbohydrate research. 相似文献
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J E Alouf 《Archives de l'Institut Pasteur de Tunis》1981,58(3):355-373
Streptolysin O is the prototype of fifteen bacterial cytolytic protein toxins elaborated by gram-positive bacteria of species Streptococcus, Clostridium, Bacillus and Listeria. These toxins share a number of common properties: they are antigenically related as shown by cross-neutralization and immunoprecipitation; their cytolytic and other reducing agents; these toxins are inactivated by cholesterol and certain related sterols. This group of oxygen-labile cytolytic toxins has been named sulfyhdryl-activated toxins or thiol-activated cytolysins. The mechanism of action of these toxins is very likely identical or at least closely similar. 相似文献
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Throughout history, humans have encountered natural toxic chemicals from the ocean environment, often through contaminated seafood. Although marine toxins can be harmful to human health and devastate local environments when they are produced during algal bloom events, they are also important biochemical research reagents and drug leads in medicine. In spite of their long history, the biosynthetic origin of many well-known marine toxins has remained elusive. New biosynthetic insights have shed light on the chemical transformations that create the complex structures of several iconic oceanic toxins. To that end, this review highlights advances made in the biosynthetic understanding of five important environmental toxins of marine origin: domoic acid, kainic acid, saxitoxin, tetrodotoxin, and polyether polyketides such as brevetoxin. 相似文献
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The cytolethal distending toxins (CDTs) constitute the most recently discovered family of bacterial protein toxins. CDTs are unique among bacterial toxins as they have the ability to induce DNA double strand breaks (DSBs) in both proliferating and nonproliferating cells, thereby causing irreversible cell cycle arrest or death of the target cells. CDTs are encoded by three linked genes (cdtA, cdtB and cdtC) which have been identified among a variety of Gram-negative pathogenic bacteria. All three of these gene products are required to constitute the fully active holotoxin, and this is in agreement with the recently determined crystal structure of CDT. The CdtB component has functional homology with mammalian deoxyribonuclease I (DNase I). Mutation of the conserved sites necessary for this catalytic activity prevents the induction of DSBs as well as all subsequent intoxication responses of target cells. CDT is endocytosed via clathrin-coated pits and requires an intact Golgi complex to exert the cytotoxic activity. Several issues remain to be elucidated regarding CDT biology, such as the detailed function(s) of the CdtA and CdtC subunits, the identity of the cell surface receptor(s) for CDT, the final steps in the cellular internalization pathway, and a molecular understanding of how CDT interacts with DNA. Moreover, the role of CDTs in the pathogenesis of diseases still remains unclear. 相似文献
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Magda A. Rogowska-van der Molen Aileen Berasategui-Lopez Silvia Coolen Robert S. Jansen Cornelia U. Welte 《Environmental microbiology》2023,25(12):2988-3010
Plants produce a variety of secondary metabolites in response to biotic and abiotic stresses. Although they have many functions, a subclass of toxic secondary metabolites mainly serve plants as deterring agents against herbivores, insects, or pathogens. Microorganisms present in divergent ecological niches, such as soil, water, or insect and rumen gut systems have been found capable of detoxifying these metabolites. As a result of detoxification, microbes gain growth nutrients and benefit their herbivory host via detoxifying symbiosis. Here, we review current knowledge on microbial degradation of toxic alkaloids, glucosinolates, terpenes, and polyphenols with an emphasis on the genes and enzymes involved in breakdown pathways. We highlight that the insect-associated microbes might find application in biotechnology and become targets for an alternative microbial pest control strategy. 相似文献
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Insecticidal toxins of Bacillus thuringiensis 总被引:3,自引:0,他引:3
Peter Lüthy 《FEMS microbiology letters》1980,8(1):1-7
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Many mono or multicellular organisms secrete soluble proteins, referred to as protein toxins, which alter the behavior of foreign, or target cells, possibly leading to their death. These toxins affect either the cell membrane by forming pores or modifying lipids, or some intracellular target. To reach this target, they must cross one of the cellular membranes, generally that of an intracellular organelle. As described in this minireview, lipids play crucial roles in the intoxication process of most if not all toxins, by allowing/promoting binding, endocytosis, trafficking and/or translocation into the cytoplasm. 相似文献
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Shiga toxins and apoptosis 总被引:9,自引:0,他引:9
The enteric pathogens Shigella dysenteriae serotype 1 and Shiga toxin-producing Escherichia coli (STEC) cause bloody diarrheal diseases that may progress to life-threatening extraintestinal complications. Although the S. dysenteriae and STEC differ in the expression of a number of virulence determinants, they share the capacity to produce one or more potent cytotoxins, called Shiga toxins (Stxs). Following the ingestion of the organisms, the expression of Stxs is critical for the development of vascular lesions in the colon, kidneys and central nervous system. It has been known for some time that following the intracellular routing of Stxs to the endoplasmic reticulum and nuclear membrane, the toxins translocate into the cytoplasm and target ribosomes for damage. However, numerous recent studies have shown that Stxs trigger programmed cell death signaling cascades in intoxicated cells. The mechanisms of apoptosis induction by these toxins are newly emerging, and the data published to date suggest that the toxins may signal apoptosis in different cells types via different mechanisms. Here we review the Stxs and the known mechanistic aspects of Stx-induced apoptosis, and present a model of apoptosis induction. 相似文献