title: Structure of lipid A from a stem-nodulating bacterium Azorhizobium caulinodans.
abstract: The structure of the lipid A of the lipopolysaccharide (LPS) from Azorhizobium caulinodans, a symbiont of the tropical legume Sesbania rostrata, was investigated by chemical compositional analyses, mass spectrometry, as well as 1D and 2D NMR spectroscopy techniques. The lipid A backbone was composed of a β-(1→6)-linked 2,3-diamino-2,3-dideoxy-D-glucopyranose (GlcpN3N) disaccharide and α-D-glucuronic acid (GlcpA). Nuclear magnetic resonance spectroscopy revealed that the GlcpA was connected to the reducing end of the diaminosugar disaccharide via an α-(1→1) glycosidic bond. The lipid A was deprived of phosphate residues. ESI-MS analysis showed that the lipid A preparation was a mixture of molecules due to the occurrence of different acylation patterns. The GlcpN3N disaccharide backbone was N-acylated at the C-2, C-3, C-2' and C-3' positions with 3-OH-18:0, 3-OH-14:0, 3-OH-20:1 and 3-OH-14:0 fatty acids, respectively. Nonpolar fatty acids as well as 3-OH-18:0 were found to be ester-linked. They were attached to hydroxyl groups of primary 3-OH fatty acids giving three acyloxyacyl moieties. Thus, the complete lipid A from A. caulinodans comprised seven acyl residues. Part of the lipid A molecules was esterified by 3-methoxybutyric acid. Azorhizobium caulinodans did not incorporate ω-1 hydroxylated very long chain fatty acids (e.g., 27-OH-28:0) into the lipid A, which makes this variant of endotoxin unusual among rhizobial lipids A.
authors.affiliation: Department of Genetics and Microbiology, Maria Curie-Sklodowska University, 19, Akademicka St., 20-033 Lublin, Poland. adam.choma@poczta.umcs.lublin.pl
authors.forename: Adam
authors.initials: A
authors.lastname: Choma
authors.forename: Iwona
authors.initials: I
authors.lastname: Komaniecka
authors.forename: Anna
authors.initials: A
authors.lastname: Turska-Szewczuk
authors.forename: Witold
authors.initials: W
authors.lastname: Danikiewicz
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Spolnik
mesh_terms: D020599:Azorhizobium caulinodans / Q000737:chemistry* / Q000502:physiology*; D002240:Carbohydrate Sequence; D005227:Fatty Acids / Q000737:chemistry; D008050:Lipid A / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D018547:Plant Stems / Q000737:chemistry* / Q000502:physiology*
chemical_list: D005227:Fatty Acids; D008050:Lipid A