Structural Characterization of an Oligosaccharide Made by Neisseria sicca

Neisseria sicca 4320 expresses two carbohydrate-containing components with sodium dodecyl sulfate-polyacrylamide gel electrophoresis mobilities that resemble those of lipooligosaccharide and lipopolysaccharide. Using matrix-assisted laser desorption ionization—time of flight and electrospray ionization mass spectrometry, we characterized a disaccharide carbohydrate repeating unit expressed by this strain. Gas chromatography identified the sugars composing the unit as rhamnose andN -acetyl-d -glucosamine. Glycosidase digestion confirmed the identity of the nonreducing terminal sugar of the disaccharide and established its β-anomeric configuration. Mass spectrometry analysis and lectin binding were used to verify the linkages within the disaccharide repeat. The results revealed that the disaccharide repeat is [-4) β-l -rhamnose (1-3) β-N -acetyl-d -glucosamine (1-] with anN -acetyl-d -glucosamine nonreducing terminus. This work is the first structural characterization of a molecule that possesses rhamnose in the genusNeisseria .