Structural Studies on the D-Arabinose-Containing Lipid A from Rhodospirillum tenue 2761

Abstract

Structural studies carried out on the isolated free lipid A of Rhodospirillum tenue 2761 revealed a new type of structure for this lipid. The lipid A backbone of 1′,6-linked glucosamine disaccharide (central disaccharide) is substituted by three different sugar residues: the non-reducing end of the disaccharide by 4-amino-4-deoxy-l-arabinose 1-phosphate and its reducing end glycosidically by d-arabinofuranose 1-phosphate; further, the reducing glucosamine of the disaccharide is branched to a third glucosamine residue by a 1”,4-glycosidic linkage. The amino and the hydroxyl groups of the central disccharide are acylated by 3-hydroxydecanoic acid (amide-linked) and palmitic and myristic acids (ester-linked). Neither amino nor hydroxyl groups of the three external sugar residues are acylated. The results suggest the following chemical structure for the lipid A of R. tenue 2761:

Abbreviations

GlcN

d-glucosamine

AraN

4-amino-4-deoxy-l-arabinose

Araf

D-arabinofuranose

Enzymes

 

Alkaline phosphatase (EC 3.1.3.1)

 

l-amino acid oxidase (EC 1.4.3.2)