Chemical structure of the lipid A component of the lipopolysaccharide from a Proteus mirabilis Re‐mutant

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Abstract
The chemical structure of the lipid A component from the lipopolysaccharide of a Proteus mirabilis Re‐mutant (strain R45) was analysed. It consists of a β(1–6)‐linked d‐glucosamine disaccharide which carries two phosphate groups, one being ester‐linked to position 4′ of the nonreducing glucosaminyl residue and the other being bound to the glycosidic hydroxyl group of the reducing glucosaminyl residue. The ester‐bound phosphate group is quantitatively substituted by a 4‐amino‐4‐deoxy‐l‐arabinopyranosyl residue, the glycosidic phosphoryl group appears to be unsubstituted. Two available hydroxyl groups of the disaccharadide (probably at positions 3 and 3) are acylated by approximately 1 mol each of (R)‐3‐tetradecanoyloxytetradecanoic and (R)‐3‐hydroxytetradecanoic acid/mol. The amino group of the nonreducing glucosaminyl residue carries (R)‐3‐tetradecanoyloxytetradecanoic and that of the reducing residue (R)‐3‐hydroxytetradecanoic acid. In addition smaller amounts of (R)‐3‐hexadecanoyloxytetradecanoic acid are present in amide linkage. The attachment site of the oligosaccharide portion to lipid A was also investigated. It was found that the hydroxyl group at position 6′ of the nonreducing glucosaminyl residue carries 3‐deoxy‐d‐manno‐octulosonic acid. This indicates that the saccharide portion in this Proteus lipopolysaccharide is linked to lipid A via the primary hydroxyl group in position 6′.