TAILIEUCHUNG - Báo cáo Y học: Osmoregulated periplasmic glucans of the free-living photosynthetic bacterium Rhodobacter sphaeroides

The osmoregulated periplasmic glucans (OPGs) produced byRhodobacter sphaeroides, a free-living organism, were isolated by trichloracetic acid treatment and gel permeation chromatography. Compounds obtained were characterized by compositional analysis, matrix-assisted laser desorption ionization mass spectrometry and nuclear magnetic . sphaeroidespredominantly synthesizes acyclic glucan containing 18 glucose residues that canbe substituted by one to seven succinyl esters residues at the C6position of some of the glucose residues, and by one or two acetyl resi-dues | Eur. J. Biochem. 269 2464-2472 2002 FEBS 2002 doi Osmoregulated periplasmic glucans of the free-living photosynthetic bacterium Rhodobactersphaeroides Philippe Talaaa1. Virainie Coaez1. Jean-Michel Wieruszeski2 Bernd Stahl3 Jerome Lemoine1 Guy Lippens2 and Jean-Pierre Bohin1 1 Unite de Glycobiologie Structural et Fonctionnelle CNRS UMR8576 Universite des Sciences et Technologies de Lille Villeneuve d Ascq France 2CNRS UMR8525 Institut de Biologie de Lille Institut Pasteur de Lille France 3Milupa GmbH Co. KG Research nnternaiional Friedrichsdorf Gm-iany The osmoregulated periplasmic glucans OPGs produced by Rhodobactée sph roides a free-living organism were isolated by trichloracetic acid treatment and gel permeation chromatography. Compounds obtained were characterized by compositional analysis matrix-assisted laser desorption ionization mass spectrometry and nuclear magnetic resonance. R. sphaéeoidés predominantly synthesizes a cyclic glucan containing 18 glucose residues that can be substituted by one to seven succinyl esters residues at the C6 position of some of the glucose residues and by one or two acetyl residues. The glucans were subjected to a mild alkaline treatment in order to remove the succinyl and acetyl substituents analyzed by MALDI mass spectrometry and purified by high-performance anion-exchange chromatography. Methylation analysis revealed that this glucan is linked by 17 1 2 glycosidic bonds and one 1 6 glycosidic bond. Homo-nuclear and 1H 13C heteronuclear NMR experiments revealed the presence of a single a-1 6 glycosidic linkage whereas all other glucose residues are linked. The different anomeric proton signals allowed a complete sequence-specific assignment of the glucan. The structural characteristics of this glucan are very similar to the previously described OPGs of Ralstonia solanacearum and Xanthomonas campestris except for its different size and the presence of substituents. Therefore similar OPGs

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