Structural analysis of lipopolysaccharides from Haemophilus influenzae serotype f - Structural diversity observed in three strains

• Structural elucidation of the lipopolysaccharide (LPS) from three serotype f Haemophilus influenzae clinical isolates RM6255, RM7290 and RM6252 has been achieved using NMR spectroscopy techniques and ESI-MS on O-deacylated LPS and core oligosaccharide material (OS) as well as ESI-MSn on permethylated dephosphorylated OS. This is the first study to report structural details on LPS from serotype f strains. We found that the LPSs of all strains were highly heterogeneous mixtures of glycoforms expressing the common H. influenzae structural element l-alpha-d-Hepp -(1-->2)-[P Etn-->6]-l-alpha-d-Hepp -(1-->3)-[beta-d-Glcp -(1-->4)]-l-alpha-d-Hepp -(1-->5)-[PP Etn-->4]-alpha-Kdo-(2-->6)-lipid A with variable length of OS chains linked to each of the heptoses. The terminal heptose (HepIII) in RM6255 is substituted at the O-3 position by a beta-d-Glcp residue whereas HepIII in strains RM7290 and RM6252 is substituted at O-2 by the globoside unit (alpha-d-Galp -(1-->4)-beta-d-Galp -(1-->4)-beta-d-Glc) or truncated versions thereof. The central heptose (HepII) is substituted by an alpha-d-Galp -(1-->4)-beta-d-Galp -(1-->4)-beta-d-Glcp -(1-->4)-alpha-d-Glcp unit in RM7290 and RM6252 or truncated versions thereof. Strain RM6255 does not express galactose in its LPS and only shows a cellobiose unit elongating from HepII (beta-d-Glcp -(1-->4)-alpha-d-Glcp ). ESI-MSn on dephosphorylated and permethylated OS provided information on the existence of additional minor isomeric glycoforms.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Haemophilus influenzae

lipopolysaccharide

NMR

ESI-MS

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