The structure of the nonreducing terminal groups in the O-specific polysaccharides from two strains of Bordetella bronchiseptica

The structures of the polysaccharide chains of the LPS from Bordetella bron chiseptica strains 110H and Bp512 were analysed by NMR spectroscopy and mas s spectrometry The polysaccharides consist of alpha-(1-4)-linked 2,3-diacet amido-2,3-dideoxy-L-galacturonic acid repeating units. Polysaccharides from both strains have 2,3,4-triamino-2,3,4-trideoxy-alpha -galacturonamide der ivatives at their nonreducing ends, a monosaccharide identified for the fir st time in nature. The polymers from the two strains differ in the nature o f the acylation of the amino groups of this monosaccharide. In the strain 1 10H, the residue is formylated at positions 3 and 4, and has N-formyl-L-ala nyl or L-alanyl substituents at N-2. In the strain Bp512, the amino group a t position 2 is acetylated, at position 3 it is formylated, and the amino g roup at position 4 bears a 2-methoxypropionyl substituent. The distribution of the acyl groups was determined from long range H-1-C-13 correlation (HM BC) NMR spectra. Measurement of the spectra under different pH conditions s howed that carboxyl groups of the inner uronic acid residues of the polymer ic chain are free, and that carboxyl groups of the terminal residues are am idated. These conclusions were confirmed by the results of mass spectrometr ic analysis.