CHARACTERIZATION OF A NOVEL BRANCHED TETRASACCHARIDE OF 3-DEOXY-D-MANNO-OCT-2-ULOPYRANOSONIC ACID - THE STRUCTURE OF THE CARBOHYDRATE BACKBONE OF THE LIPOPOLYSACCHARIDE FROM ACINETOBACTER-BAUMANNII STRAIN NCTC-10303 (ATCC-17904)

For the first time, the tetrasaccharide Kdo alpha 2-->5Kdo alpha 2-->5 (Kdo alpha 2-->4)Kdo (Kdo is 3-deoxy-D-manno-oct-2-ulopyranosonic acid ) has been identified in a bacterial lipopolysaccharide (LPS), i.e. in the core region of LPS from Acinetobacter baumannii NCTC 10303, The L PS was analyzed using compositional analysis, mass spectrometry, and N MR spectroscopy. The disaccharide D-GlcpN beta 1-->6D-GlcpN, phosphory lated at O-1 and O-4', was identified as the carbohydrate backbone of the lipid A. The Kdo tetrasaccharide is attached to O-6' of this disac charide and is further substituted by short L-rhamnoglycans of varying length and by the disaccharide D-GlcpNAc alpha 1-->4D-GlcpNA (GlcpNA, 2-amino-2-deoxy-glucopyranosuronic acid). The core region is not subs tituted by phosphate residues and represents a novel core type of bact erial LPS, The complete carbohydrate backbone of the LPS is shown in S tructure I as follows: [GRAPHICS] where Rha is rhamnose, Except were i ndicated, monosaccharides possess the D-configuration. Sugars marked w ith an asterisk are present in non-stoichiometric amounts.