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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Glycoconjugate journal 16 (1999), S. 205-212 
    ISSN: 1573-4986
    Keywords: oligosaccharides ; glycosyltransferases ; glycobiology ; N-acetyllactosamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Scientific and commercial interest in oligosaccharides is increasing, but their availability is limited as production relies on chemical or chemo-enzymatic synthesis. In search for a more economical, alternative procedure, we have investigated the possibility of producing specific oligosaccharides in E. coli that express the appropriate glycosyltransferases. The Azorhizobium chitin pentaose synthase NodC (a β(1,4)GlcNAc-transferase), and the Neisseria β(1,4)galactosyltransferase LgtB, were co-expressed in E. coli. The major oligosaccharide isolated from the recombinant strain, was subjected to LC-MS, FAB-MS and NMR analysis, and identified as βGal(1,4)[βGlcNAc(1,4)]4GlcNAc. High cell density culture yielded more than 1.0 gr of the hexasaccharide per liter of culture. The compound was found to be an acceptor in vitro for βGal(1,4)GlcNAc α(1,3)galactosyltransferase, which suggests that the expression of additional glycosyltransferases in E. coli will allow the production of more complex oligosaccharides.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 9 (1993), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Azorhizobium caulinodans strain ORS571 nodu-lation genes nodSUIJ were located downstream from nodABC. Complementation data and transcriptional analysis suggest that nodABCSUIJ form a single operon. Mutants with Tn5 insertions in the genes nodS, nodU, and nodJ were delayed in nodulation of Sesbania rostrata roots and stems. The NodS amino acid sequences of ORS571, Bradyrhizobium japonicum, and Rhizobium sp. strain NGR234, contain a consensus with similarity to 5-adenosylmethionine (SAM)-utilizing methyltransferases. A naringenin-inducible nodS-dependent protein of approximately 25kDa could be cross-linked to radiolabelled SAM. By applying L-[methyl-3H]-methionine in vivo. Nod factors of ORS571, known to be N-methylated, could be labelled in wild type and nodU mutants but not in nodS mutants. Therefore, we propose that NodS is a SAM-utilizing methyltransferase involved in Nod factor synthesis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The soil fungus Trichoderma harzianum is a mycoparasitic fungus known for its use as a biocontrol agent of phytopathogenic fungi. Among other factors, Trichoderma produces a series of antibiotics and fungal cell wall-degrading enzymes. These enzymes are believed to play an important role in mycoparasitism. Among the hydrolytic enzymes, we have identified a basic proteinase (Prb1) which is induced by either autoclaved mycelia, fungal cell wall preparation or chitin; however, the induction does not occur in the presence of glucose. The proteinase was purified and biochemically characterized as a serine proteinase of 31 kDa and pl 9.2. Based on the sequence of three internal peptides, synthetic oligonudeotide probes were designed. These probes allowed subsequent isolation of a cDNA and its corresponding genomic clone. The deduced amino acid sequence indicates that the proteinase is synthesized as a pre-proenzyme and allows its classification as a serine proteinase. Northen analysis shows that the induction of this enzyme is due to an increase in the corresponding mRNA level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Osney Mead, Oxford OX2 0EL, UK : Blackwell Scientific Publications
    Molecular microbiology 17 (1995), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In response to phenolic compounds exuded by the host plant, symbiotic Rhizobium bacteria produce signal molecules (Nod factors), consisting of lipochitooligosaccharides with strain-specific substitutions. In Azorhizobium caulinodans strain ORS571 these modifications are an O-arabinosyl group, an O-carbamoyl group, and an N-methyl group. Several lines of evidence indicate that the nodS gene located in the nodABCSUIJ operon is implicated in the methylation of Nod factors. Previously we have shown that NodS is an S-adenosyl-l-methionine (SAM)-binding protein, essential for the l-[3H-methyl]-methionine labelling of ORS571 Nod factors in vivo. Here, we present an in vitro assay showing that NodS from either A. caulinodans or Rhizobium species NGR234 methylates end-deacetylated chitooligosaccharides, using [3H-methyl]-SAM as a methyl donor. The enzymatic and SAM-binding activity were correlated with the nodS gene and localized within the soluble protein fraction. The A. caulinodans nodS gene was expressed in Escherichia coli and a glutathione-S-transferase—NodS fusion protein purified. This protein bound SAM and could methylate end-deacetylated chitooligosaccharides, but could not fully methylate acetylated chitooligosaccharides or unmethylated lipo-chitooligosaccharides. These data implicate that the methylation step in the biosynthesis pathway of ORS571 Nod factors occurs after deacetylation and prior to acylation of the chitooligosaccharides.
    Type of Medium: Electronic Resource
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