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AB Toxin

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Jorge E. Galán – One of the best experts on this subject based on the ideXlab platform.

  • Structure and function of the Salmonella Typhi chimaeric A_2B_5 typhoid Toxin
    Nature, 2013
    Co-Authors: Jeongmin Song, Jorge E. Galán
    Abstract:

    The biological basis for the pathogenic properties of Salmonella enterica serovar Typhi ( S . Typhi) is largely unknown. S . Typhi causes life-threatening systemic infections known as typhoid fever, whereas most other Salmonella enterica serotypes are either harmless or associated with less-serious gastric infections or food poisoning. This study shows that administration of typhoid Toxin, a novel AB Toxin composed of two A subunits unique to S . Typhi, reproduces many of the acute symptoms of typhoid fever. The authors go on to identify carbohydrates on cell-surface glycoproteins as receptors for typhoid Toxin and determine the Toxin‘s crystal structure, providing insights into these interactions. Theses advances suggest that antiToxin-based therapeutics may be effective in treating typhoid. Unlike most salmonellae, Salmonella enterica serovar Typhi causes life-threatening systemic infections known as typhoid fever, for which the molecular basis is unknown; here administration of typhoid Toxin produced by S. Typhi reproduces many of the acute symptoms of typhoid fever, carbohydrates on cell surface glycoproteins are identified as receptors for typhoid Toxin and the Toxin’s crystal structure is determined, providing insights into these interactions. Salmonella enterica serovar Typhi ( S. Typhi) differs from most other salmonellae in that it causes a life-threatening systemic infection known as typhoid fever^ 1 . The molecular bases for its unique clinical presentation are unknown^ 2 . Here we find that the systemic administration of typhoid Toxin, a unique virulence factor of S. Typhi, reproduces many of the acute symptoms of typhoid fever in an animal model. We identify specific carbohydrate moieties on specific surface glycoproteins that serve as receptors for typhoid Toxin, which explains its broad cell target specificity. We present the atomic structure of typhoid Toxin, which shows an unprecedented A_2B_5 organization with two covalently linked A subunits non-covalently associated to a pentameric B subunit. The structure provides insight into the Toxin’s receptor-binding specificity and delivery mechanisms and reveals how the activities of two powerful Toxins have been co-opted into a single, unique Toxin that can induce many of the symptoms characteristic of typhoid fever. These findings may lead to the development of potentially life-saving therapeutics against typhoid fever.

  • Cytolethal distending Toxin: limited damage as a strategy to modulate cellular functions
    Trends in Microbiology, 2002
    Co-Authors: Maria Lara-tejero, Jorge E. Galán
    Abstract:

    ABstract The coevolution of bacterial pathogens and their hosts has contributed to the development of very complex and sophisticated functional pathogen–host interfaces. Thus, well-adapted pathogens have evolved a variety of strategies to manipulate host cell functions precisely. For example, a group of unrelated Gram-negative pathogenic bacteria have evolved a Toxin, known as cytolethal distending Toxin (CDT), that has the ABility to control cell cycle progression in eukaryotic cells. Recent studies have identified CdtB as the active subunit of the CDT holoToxin. Through its nuclease activity, CdtB causes limited DNA damage, thereby triggering the DNA-damage response that ultimately results in the observed arrest of the cell cycle. In addition, it has been estABlished that CDT is a tripartite AB Toxin in which CdtB is the active ‘A’ subunit and CdtA and CdtC constitute the heterodimeric ‘B’ subunit required for the delivery of CdtB into the target cell. The mechanism of action of CDT suggests that the infliction of limited damage could be a strategy used by pathogenic bacteria to modulate host cell functions.

Hiroshi Otani – One of the best experts on this subject based on the ideXlab platform.

  • host specific AB Toxin production by germinating spores of alternaria brassicicola is induced by a host derived oligosaccharide
    Physiological and Molecular Plant Pathology, 2005
    Co-Authors: Hajime Akamatsu, Motoichiro Kodama, Hiromitsu Nakajima, Toshinari Kawada, Hiroshi Otani
    Abstract:

    ABstract The phytopathogenic fungus Alternaria brassicicola is the causal agent of black spot disease of Brassica plants and produces a host-specific protein Toxin named ABToxin. ABToxin is released from spores germinating only on host leaves. In this study, we found a factor for inducing ABToxin production that is released from host leaves after spore germination has begun. GC and GC–MS analyses of the compound purified by gel filtration chromatography demonstrated that it is an oligosaccharide of 1.3 kDa. This is the first evidence that host-specific Toxin production by germinating spores of a fungal pathogen is induced by recognition of host-derived factors.

  • Specific inhibition of spore germination of Alternaria brassicicola by fistupyrone from Streptomyces sp. TP-A0569
    Journal of General Plant Pathology, 2003
    Co-Authors: Evelyn Aigho Aremu, Hajime Akamatsu, Motoichiro Kodama, Tamotsu Furumai, Yasuhiro Igarashi, Yukio Sato, Hiroshi Otani
    Abstract:

    Fistupyrone (FP), a metABolite from Streptomyces sp. TP-A0569, inhibited the in vivo infection of Chinese cABbage seedlings by Alternaria brassicicola. To detect the possible action sites of FP, the effect of FP on the infection behavior of A. brassicicola and A. alternata was investigated. When spores of A. brassicicola were suspended in FP solution and inoculated on host leaves, FP at 0.1 ppm significantly inhibited spore germination, appressorial formation, and infection hypha formation of A. brassicicola . Host-specific ABToxin production and lesion formation by A. brassicicola spores were also reduced significantly by treatment with FP 1 ppm. The effect of FP seemed to be irreversible because significant washing of FP-treated spores with distilled water (DW) did not change the inhibitory effects. In contrast, A. alternata isolates such as Japanese pear pathotype, apple pathotype, and saprophyte behaved almost equally in both FP- and DW-treated spores. Mycelial dry weight in potato dextrose broth and mycelial diameters on potato dextrose agar, gelatin glucose agar, and Czapek solution agar of both A. brassicicola and A. alternata were not different with or without addition of FP. These results indicate that FP at low concentrations has a fungicidal effect on spores of A. brassicicola but not on spores of A. alternata ; FP also does not affect the vegetative phase of these fungi.

  • Production of a host-specific Toxin by germinating spores ofAlternaria brassicicola☆
    Physiological and Molecular Plant Pathology, 1998
    Co-Authors: Hiroshi Otani, Motoichiro Kodama, A. Kohnobe, Keisuke Kohmoto
    Abstract:

    ABstract Spore suspensions ofAlternaria brassicicolapathogenic toBrassicaspp. were incubated on the surface ofBrassicaleaves. The spore germination fluid was collected and examined for biological activity. In a detached leaf assay, the fluid induced water-soaking symptoms followed by brown necrotic lesions onBrassicaleaves susceptible to the pathogen but did not cause visible symptoms on non-host leaves. When spores of the non-pathogenic speciesAlternaria alternatawere combined with the fluid and inoculated on the leaves, the spores could invadeBrassicaleaves, just as the pathogen did. These results indicate thatA. brassicicolaproduces a host-specific Toxin(s) and releases it during spore germination on the leaves. Toxin activity of the fluid was retained by an ultrafiltration membrane with a 5 kDa cut off. The Toxin was purified by ion exchange chromatography and gel filtration HPLC. The molecular weight of the Toxin was estimated to be 35 kDa by SDS-polyacrylamide gel electrophoresis. The activity of the Toxin was heat lABile and was also lost after treatment with proteinase K. Thus, the Toxin named ABToxin is probABly a protein, the first described among the many host-specific Toxins produced byAlternariaspecies.

Jeongmin Song – One of the best experts on this subject based on the ideXlab platform.

  • Structure and function of the Salmonella Typhi chimaeric A_2B_5 typhoid Toxin
    Nature, 2013
    Co-Authors: Jeongmin Song, Jorge E. Galán
    Abstract:

    The biological basis for the pathogenic properties of Salmonella enterica serovar Typhi ( S . Typhi) is largely unknown. S . Typhi causes life-threatening systemic infections known as typhoid fever, whereas most other Salmonella enterica serotypes are either harmless or associated with less-serious gastric infections or food poisoning. This study shows that administration of typhoid Toxin, a novel AB Toxin composed of two A subunits unique to S . Typhi, reproduces many of the acute symptoms of typhoid fever. The authors go on to identify carbohydrates on cell-surface glycoproteins as receptors for typhoid Toxin and determine the Toxin‘s crystal structure, providing insights into these interactions. Theses advances suggest that antiToxin-based therapeutics may be effective in treating typhoid. Unlike most salmonellae, Salmonella enterica serovar Typhi causes life-threatening systemic infections known as typhoid fever, for which the molecular basis is unknown; here administration of typhoid Toxin produced by S. Typhi reproduces many of the acute symptoms of typhoid fever, carbohydrates on cell surface glycoproteins are identified as receptors for typhoid Toxin and the Toxin’s crystal structure is determined, providing insights into these interactions. Salmonella enterica serovar Typhi ( S. Typhi) differs from most other salmonellae in that it causes a life-threatening systemic infection known as typhoid fever^ 1 . The molecular bases for its unique clinical presentation are unknown^ 2 . Here we find that the systemic administration of typhoid Toxin, a unique virulence factor of S. Typhi, reproduces many of the acute symptoms of typhoid fever in an animal model. We identify specific carbohydrate moieties on specific surface glycoproteins that serve as receptors for typhoid Toxin, which explains its broad cell target specificity. We present the atomic structure of typhoid Toxin, which shows an unprecedented A_2B_5 organization with two covalently linked A subunits non-covalently associated to a pentameric B subunit. The structure provides insight into the Toxin’s receptor-binding specificity and delivery mechanisms and reveals how the activities of two powerful Toxins have been co-opted into a single, unique Toxin that can induce many of the symptoms characteristic of typhoid fever. These findings may lead to the development of potentially life-saving therapeutics against typhoid fever.