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A sialylated lacto-N-neotetraose (Sial-lNnT) structural unit was identified and structurally characterized in the lipo-polysaccharide (LPS) from the genome-sequenced strain Road (RM118) of the human pathogenHaemophilus influ-enzaegrown in the presence of sialic acid. A combination of molecular genetics, MS and NMR spectroscopy techniques showed that this structural unit extended from the proximal heptose residue of the inner core regionof theLPSmolecule. | Eur. J. Biochem. 269 4009-4019 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03090.x Identification and structural characterization of a sialylated lacto-N-neotetraose structure in the lipopolysaccharide of Haemophilus influenzae Andrew D. Cox1 Derek W. Hood2 Adele Martin1 Katherine M. Makepeace2 Mary E. Deadman2 Jianjun Li1 Jean-Robert Brisson1 E. Richard Moxon2 and James C. Richards1 1 Institute for Biological Sciences National Research Council Ottawa Canada 2University of Oxford Department of Paediatrics Weatherall Institute for Molecular Medicine John Radcliffe Hospital Oxford UK A sialylated lacto-N-neotetraose Sial-lNnT structural unit was identified and structurally characterized in the lipopolysaccharide LPS from the genome-sequenced strain Road RM118 of the human pathogen Haemophilus influenzae grown in the presence of sialic acid. A combination of molecular genetics MS and NMR spectroscopy techniques showed that this structural unit extended from the proximal heptose residue of the inner core region of the LPS molecule. The structure of the Sial-lNnT unit was identical to that found in meningococcal LPS but glycoforms containing truncations of the Sial-lNnT unit comprising fewer resid Lies than the complete oligosaccharide component were not detected. The findingof sialylated lgycoforms that were either fully extended or absent suggests a novel biosynthetic feature for addingthe terminal tetrasaccharide unit of the Sial-lNnT to the glycose acceptor at the proximal inner core heptose. Keywords Haemophilus influenzae LPS mass spectrometry NMR sialic acid. Haemophilus influenzae remains an important cause of disease worldwide. Encapsulated strains can cause invasive bacteraemic infections such as septicemia and strains lacking a capsule so-called nontppebble strains NTHi are a common cause of otitis media and acute lower respiratory tract infections 1 . Lipopolysaccharide LPS is critical to the integrity and functioning of the cell wall of H. influenzae and as
