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Structural and biological characterisation of a novel tetra-acyl lipid A from Escherichia coli F515 lipopolysaccharide acting as endotoxin antagonist in human monocytesResearch Center Borstel, Center for Medicine and Biosciences, Borstel, Germany, uzaehr{at}fz-borstel.de
Research Center Borstel, Center for Medicine and Biosciences, Borstel, Germany
Research Center Borstel, Center for Medicine and Biosciences, Borstel, Germany
Research Center Borstel, Center for Medicine and Biosciences, Borstel, Germany
Research Center Borstel, Center for Medicine and Biosciences, Borstel, Germany We here report on the structural analysis of a novel tetra-acyl lipid A (LAtetra) isolated from Escherichia coli deep rough (Re)-mutant strain F515. In addition to the biologically active hexa-acyl E. coli-type lipid A (compound 506), this incompletely acylated lipid A was found to be also present in the native LPS. Its structure was studied without further derivatisation by chemical analysis, matrix-assisted laser desorption/ionization mass spectrometry, and one- and two-dimensional 1H- and 13C-NMR spectroscopy. It was found to be structurally distinct from the tetraacyl lipid A biosynthetic precursor Ia (compound 406) in lacking the primary (R)-3-hydroxytetradecanoic acid 14:0(3-OH) in position 3' ester-linked to the `non-reducing' glucosamine (GlcN II). The hydroxyl group at the (R)-3-hydroxytetradecanoic acid attached to position 2' of GlcN II was found to be substituted by dodecanoic acid (12:0), thus forming a dodecanoyloxytetradecanoyl residue 14:0[3- O(12:0)]. The acylation pattern at the `reducing' GlcN I was identical to that of compound 406 in having two primary (R)-3-hydroxy tetradecanoic acid residues [14:0(3-OH)] attached to positions 3 (ester-linked) and 2 (amide-linked), respectively. In human mononuclear cells (hMNC) the new LAtetra antagonized LPS-induced release of interleukine-1 (IL-1), interleukine-6 (IL-6), and tumor necrosis factor (TNF) in a dose-dependant manner with identical antagonistic potency as compared with compound 406. Also like compound 406, it was found to be an agonist in murine macrophage-like J774.1 cells.
Journal of Endotoxin Research, Vol. 7, No. 2,
133-146 (2001) |
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