title: Structural characterization of the lipid A region of Aeromonas salmonicida subsp. salmonicida lipopolysaccharide.
abstract: The lipid A components of Aeromonas salmonicida subsp. salmonicida from strains A449, 80204-1 and an in vivo rough isolate were isolated by mild acid hydrolysis of the lipopolysaccharide. Structural studies carried out by a combination of fatty acid, electrospray ionization-mass spectrometry and nuclear magnetic resonance analyses confirmed that the structure of lipid A was conserved among different isolates of A. salmonicida subsp. salmonicida. All analyzed strains contained three major lipid A molecules differing in acylation patterns corresponding to tetra-, penta- and hexaacylated lipid A species and comprising 4'-monophosphorylated beta-2-amino-2-deoxy-d-glucopyranose-(1-->6)-2-amino-2-deoxy-d-glucopyranose disaccharide, where the reducing end 2-amino-2-deoxy-d-glucose was present primarily in the alpha-pyranose form. Electrospray ionization-tandem mass spectrometry fragment pattern analysis, including investigation of the inner-ring fragmentation, allowed the localization of fatty acyl residues on the disaccharide backbone of lipid A. The tetraacylated lipid A structure containing 3-(dodecanoyloxy)tetradecanoic acid at N-2',3-hydroxytetradecanoic acid at N-2 and 3-hydroxytetradecanoic acid at O-3, respectively, was found. The pentaacyl lipid A molecule had a similar fatty acid distribution pattern and, additionally, carried 3-hydroxytetradecanoic acid at O-3'. In the hexaacylated lipid A structure, 3-hydroxytetradecanoic acid at O-3' was esterified with a secondary 9-hexadecenoic acid. Interestingly, lipid A of the in vivo rough isolate contained predominantly tetra- and pentaacylated lipid A species suggesting that the presence of the hexaacyl lipid A was associated with the smooth-form lipopolysaccharide.
authors.affiliation: Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ont., Canada K1A 0R6.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Wang
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Eleonora
authors.initials: E
authors.lastname: Altman
mesh_terms: D000215:Acylation; D048409:Aeromonas salmonicida / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D005227:Fatty Acids / Q000032:analysis; D008050:Lipid A / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D005227:Fatty Acids; D008050:Lipid A