Microheterogeneity in Lipid A Demonstrated by a New Intermediate in the Biosynthesis of 3‐Deoxy‐d‐manno‐octulosonic‐acid–Lipid A

• Published in: European journal of biochemistry Vol. 81; no. 3; pp. 443 - 452
• Main Authors: LEHMANN, Volker, RUPPRECHT, Eckhard
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.1977
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1111/j.1432-1033.1977.tb11969.x

A previous report [Lehmann, Rupprecht & Osborn (1977) Eur. J. Biochem. 76, 41–49] described the characterisation of a new class of conditional lethal mutants which are temperature sensitive both in synthesis of 3‐deoxy‐d‐manno‐octulosonic acid 8‐phosphate and in growth. It was found that these mutants synthesize at restrictive temperatures lipid A intermediates consisting of glucosamine disaccharides carrying four 3‐hydroxymyristic acids and two unsubstituted phosphate groups (acidic precursor) [Lehmann (1977) Eur. J. Biochem. 75, 257–266]. The present paper describes the discovery of a new lipid A intermediate (neutral precursor) which is accumulated in the same mutant under slightly modified cultivation conditions. It differs from the acidic precursor by the presence of 4‐aminoarabinose, phosphorylethanolamine and polyamines and exhibits, like the complete lipid A structure of lipopolysaccharides, a considerable degree of intrinsic heterogeneity [Mühlradt, Wray & Lehmann (1977) Eur. J. Biochem. 81, 193–203]. Application of different degradation pathways combined with 31P nuclear magnetic resonance spectroscopy showed that in the neutral precursor 4‐aminoarabinose is linked to the ester‐bound 4‐phosphate while phosphorylethanolamine is linked to the 1‐phosphate. The presence of polyamines such as putrescine, spermidine, cadaverine and lysine suggest that some species of the neutral precursor fraction are crosslinked by ionic interaction. Evidence will be presented that the neutral precursor, like the acidic one, is an intermediate in the 3‐deoxy‐d‐manno‐octulosonic acid–lipid A synthesis. Furthermore the findings altogether support a notion in which the acidic precursor could serve as acceptor for the transfer of 4‐aminoarabinose, phosphorylethanolamine and polyamines to the glucosamine backbone structure.