polygalacturonic-acid and 2-3-diamino-2-3-dideoxyglucose

The structure of lipid A from lipopolysaccharide of Phyllobacterium trifolii PETP02

Topics: Fatty Acids; Glucosamine; Hexuronic Acids; Lipid A; Lipopolysaccharides; Magnetic Resonance Spectroscopy; Mesorhizobium; Metabolic Networks and Pathways; Phyllobacteriaceae; Sequence Homology, Amino Acid; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The chemical structure of the free lipid A isolated from Mesorhizobium huakuii IFO 15243(T) was elucidated. Lipid A is a mixture of at least six species of molecules whose structures differ both in the phosphorylation of sugar backbone and in fatty acylation. The backbone consists of a beta (1'-->6) linked 2,3-diamino-2,3-dideoxyglucose (DAG) disaccharide that is partly substituted by phosphate at position 4'. The aglycon of the DAG-disaccharide has been identified as alpha-D-galacturonic acid. All lipid A species carry four amide-linked 3-hydroxyl fatty residues. Two of them have short hydrocarbon chains (i.e. 3-OH-i-13:0) while the other two have longer ones (i.e. 3-OH-20:0). Distribution of 3-hydroxyl fatty acids between the reducing and nonreducing DAG is symmetrical. The nonpolar as well as (omega-1) hydroxyl long chain fatty acids are components of acyloxyacyl moieties. Two acyloxyacyl residues occur exclusively in the nonreducing moiety of the sugar backbone but their distribution has not been established yet. The distal DAG amide-bound fatty acid hydroxyls are not stoichiometrically substituted by ester-linked acyl components.

Topics: Alphaproteobacteria; Gas Chromatography-Mass Spectrometry; Glucosamine; Hexuronic Acids; Hydrocarbons; Lipid A; Lipids; Magnetic Resonance Spectroscopy; Models, Chemical; Phosphates; Phosphorylation; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization