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  • 1
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The ability of M-protein-positive (M+) and M-protein-negative (M−) strains (including an M− mutant lacking the structural gene for M-protein) ofStreptococcus pyogenes to attach to human pharyngeal, buccal, and tongue epithelial cells was compared. We observed that M+ strains ofS. pyogenes attached in significantly higher numbers to human pharyngeal epithelial cells than to human buccal or tongue cells. M− strains did not exhibit high-level binding to any type of epithelial cell. Also, the adhesion of an M+ and an M− strain ofS. pyogenes was low to all types of rat epithelial cells tested. The apparent differences in the surface components between human pharyngeal and buccal epithelial cells were confirmed by studies utilizing radiolabeled lectins.Ulex europaeus lectin with a specificity for fucosyl residues, andTriticum vulgaris lectin with a specificity for N-acetyl glucosamine and N-acetyl neuraminic acid residues, bound in higher amounts to human pharyngeal cells than to buccal cells. Pretreatment of pharyngeal epithelial cells with microgram quantities of highly purified type 6 M-protein or miligram quantities of lipoteichoic acid (LTA) derived fromS. pyogenes decreased the subsequent attachment of the organism. However, the binding specificities of3H-LTA were different from those of intact streptococci;3H-LTA bound comparably to human pharyngeal, buccal, and tongue epithelial cells, and it bound in higher quantities to rat epithelial cells. Also, although the adsorption ofS. pyogenes cells to pharyngeal cells was inhibited by the presence of fucose and galactose, these sugars had little effect on the binding of3H-LTA to epithelial cells. In contrast, the high adhesion of M+ strains but not M− mutants to pharyngeal cells suggested that M-protein may play an important role. This possibility was supported by the observation that3H-labeled purified type 6 M-protein bound in higher concentrations to human pharyngeal epithelial cells than to human buccal cells. Furthermore, human pharyngeal epithelial cells were estimated to contain larger numbers of binding sites for M-protein than buccal cells, whereas the affinity of M-protein was similar to both cell types. These adsorption parameters are similar to those previously established for intact streptococcal cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Intragenic recombination ; Repeats ; Antigenic and size variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary M protein, a major surface protein and virulence factor for the group A streptococcus, exhibits extraordinary size variation in strains of the same serotype (Fischetti et al. 1985). RNA sequence analysis of spontaneous M protein size variants shows that deletion mutations arise in a single strain by homologous recombination events between intragenic tandem repeats. Similar deletion and duplication events also occur in serial streptococcal isolates from a single patient and among related strains in a recent outbreak. We discuss how homologous recombination events can lead to the generation of antigenic variation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0887-3585
    Keywords: coiled-coli ; alpha-helix ; antiphagocytic ; heptad ; antigenic variation ; sequence repeats ; cell wall protein ; intermediate filaments ; myosin ; tropomyosin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: M protein is considered a virulence determinant on the streptococcal cell wall by virtue of its ability to allow the organism to resist attack by human neutrophils. The complete DNA sequence of the M6 gene from streptococcal strain D471 has allowed, for the first time, the study of the structural characteristics of the amino acid sequence of an entire M protein molecule. Predictive secondary structural analysis revealed that the majority of this fibrillar molecule exhibits strong alpha-helical potential and that, except for the ends, nonpolar residues in the central region of the molecule exhibit the 7-residue periodicity typical for coiled-coil proteins. Differences in this heptad pattern of nonpolar residues allow this central rod region to be divided into three subdomains which correlate essentially with the repeat regions A, B, and C/D in the M6 protein sequence. Alignment of the N-terminal half of the M6 sequence with PepM5, the N-terminal half of the M5 protein, revealed that 42% of the amino acids were identical. The majority of the identities were “core” nonpolar residues of the heptad periodicity which are necessary for the maintenance of the coiled coil. Thus, conservation of structure in a sequence-variable region of these molecules may be biologically significant. Results suggest that serologically different M proteins may be built according to a basic scheme: an extended central coiled-coil rod domain (which may vary in size among strains) flanked by functional end domains.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 418 (2002), S. 884-889 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The dormant and durable spore form of Bacillus anthracis is an ideal biological weapon of mass destruction. Once inhaled, spores are transported by alveolar macrophages to lymph nodes surrounding the lungs, where they germinate; subsequent vegetative expansion causes an overwhelming flood of ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 24 (2006), S. 1508-1511 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] When phages were first discovered nearly a century ago, it was immediately apparent that their potent bactericidal capacity should be harnessed to treat human infections. The industrialization of antibiotics in the 1940s, however, changed the focus of anti-infective research and development in the ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 19 (2001), S. 734-735 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Natural products formed the basis of most antibiotics in use today. But nature also provides an alternative source of antibacterial agents in the form of lytic bacteriophages—small viruses harmless to humans, but lethal to their bacterial hosts. Although the antibacterial properties of phages ...
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