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  • C-terminal amino acid sequence  (1)
  • Melastoma malabathricum L.  (1)
  • 1
    ISSN: 1573-4943
    Keywords: Botulinum neurotoxin ; N-terminal amino acid sequence ; C-terminal amino acid sequence ; surface probability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Botulinum neurotoxin (NT) is synthesized by Clostridium botulinum as about a 150-kDa single-chain polypeptide. Posttranslational modification by bacterial or exogenous proteases yielded dichain structure which formed a disulfide loop connecting a 50-kDa light chain (Lc) and 100-kDa heavy chain (Hc). We determined amino acid sequences around cleavage sites in the loop region of botulinum NTs produced by type C strain Stockholm, type D strain CB16, and type F strain Oslo by analysis of the C-terminal sequence of Lc and the N-terminal sequence of Hc. Cleavage was found at one or two sites at Arg444/Ser445 and Lys449/Thr450 for type C, and Lys442/Asn443 and Arg445/Asp446 for type D, respectively. In culture fluid of mildly proteolytic strains of type C and D, therefore, NT exists as a mixture of at least three forms of nicked dichain molecules. The NT of type F proteolytic strain Oslo showed the Arg435 as a C-terminal residue of Lc and Ala440 as an N-terminal residue of Hc, indicating that the bacterial protease cuts twice (Arg435/Lys436 and Lys439/Ala440), with excision of four amino acid residues. The location of cleavage and number of amino acid residue excisions in the loop region could be explained by the degree of exposure of amino acid residues on the surface of the molecule, which was predicted as surface probability from the amino acid sequence. In addition, the observed correlation may also be adapted to the cleavage sites of the other botulinum toxin types, A, B, E, and G.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: Al accumulator plant ; Al distribution ; Al localization ; Al-oxalate complex ; Melastoma malabathricum L. ; 27Al NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The Al accumulation mechanisms in an Al accumulator plant, Melastoma malabathricum L. (Melastoma), was investigated. Al was located in the upper epidermal cells and also distributed in mesophyll cells in leaf sections. In root sections, Al was found in all the root tissues, particularly in the epidermis and endodermis. Al concentrations in young leaves, mature leaves, old leaves, and roots were 8.0, 9.2, 14.4, and 10.1 mg g1, respectively. Approximately 45% of total Al in oldest leaves, and approximately 60% of total Al in leaves of other positions and roots were extracted in Tris-HCl buffer (pH 7.0). Since Al in the residual parts was mostly dissolved in hot 0.5 M H2SO4 containing 2% cetyl trimethylammonium bromide, residual Al seemed to consist mainly of monomeric Al and Al bound to pectic substances and hemicellulose. Al in the Tris-HCl extract consisted of non-monomeric Al (complexed form). Oxalate concentration in the Tris-HCl extract in leaves was significantly higher in the +Al treatment than in the –Al treatment and there was a positive correlation between the Al concentration and oxalate concentration. 27Al NMR spectrum of fresh leaves indicated the presence in the order of monomeric Al, Al-oxalate, Al-(oxalate)2, and Al-(oxalate)3 in intact leaves.
    Type of Medium: Electronic Resource
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