title: Evidence that the acidic polysaccharide secreted by Agrobacterium radiobacter (ATCC 53271) has a seventeen glycosyl-residue repeating unit.
abstract: The extracellular anionic polysaccharide produced by the bacterium Agrobacterium radiobacter (ATCC 53271) contains D-galactose, D-glucose, and pyruvic acid in the molar ratio 2:15:2. Analysis of the methylated polysaccharide indicated the presence of terminal, non-reducing glucosyl, 3-, 4-, 6-, 2,4-, and 4,6-linked glucosyl residues, 3-linked 4,6-O-[(S)-1-carboxyethylidene]glucosyl residues, and 3-linked galactosyl residues. Partial acid hydrolysis of the methylated polysaccharide, followed by reduction with NaB2H4 and then O-ethylation, gave a mixture of alkylated oligoglycosyl alditols that were separated by reversed-phase h.p.l.c. and analyzed by 1H-n.m.r. spectroscopy, g.l.c.-m.s., and glycosyl-linkage composition analysis. Smith degradation of the polysaccharide gave three diglycosyl alditols that were separated by semi-preparative, high-pH anion-exchange chromatography, and were analyzed by 1H-n.m.r. spectroscopy, g.l.c.-m.s., and glycosyl-linkage composition analysis. The polymer obtained by NaBH4 reduction of the periodate-oxidized polysaccharide was methylated, and the noncyclic acetals were hydrolyzed with aq. 90% formic acid to generate a mixture of partially O-methylated mono- and di-glycosyl alditols. The partially O-methylated oligoglycosyl alditols were O-ethylated. The resulting alkylated oligoglycosyl alditols were separated by reverse-phase h.p.l.c. and then characterized by 1H-n.m.r. spectroscopy, g.l.c.-m.s., and glycosyl-linkage composition analysis. The results from the studies described here provide strong evidence that the acidic polysaccharide secreted by A. radiobacter (ATCC 53271) has a heptadecasaccharide repeating unit.
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, Athens 30602.
authors.forename: M A
authors.initials: MA
authors.lastname: O'Neill
authors.forename: P D
authors.initials: PD
authors.lastname: Robison
authors.forename: K J
authors.initials: KJ
authors.lastname: Chou
authors.forename: A G
authors.initials: AG
authors.lastname: Darvill
authors.forename: P
authors.initials: P
authors.lastname: Albersheim
mesh_terms: D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D005690:Galactose / Q000032:analysis; D005947:Glucose / Q000032:analysis; D006027:Glycosides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D011773:Pyruvates / Q000032:analysis; D019289:Pyruvic Acid; D012231:Rhizobium / Q000737:chemistry*
chemical_list: D006027:Glycosides; D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; D011773:Pyruvates; D019289:Pyruvic Acid; D005947:Glucose; D005690:Galactose