Structural analysis of Francisella tularensis lipopolysaccharide

• Published in: European journal of biochemistry Vol. 269; no. 24; pp. 6112 - 6118
• Main Authors: Vinogradov, Evgeny, Perry, Malcolm B, Conlan, J. Wayne
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.12.2002
• Subjects: acid hydrolysis; acids; Carbohydrate Sequence; chemical structure; core; Fatty Acids - metabolism; Francisella tularensis; Francisella tularensis - metabolism; glucosamine; Hydrofluoric Acid - metabolism; lipid A; Lipid A - chemistry; lipopolysaccharide; Lipopolysaccharides - chemistry; Magnetic Resonance Spectroscopy; Mass Spectrometry; Models, Chemical; Molecular Sequence Data; nuclear magnetic resonance spectroscopy; oligosaccharides; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1046/j.1432-1033.2002.03321.x

The structure of the lipid A and core region of the lipopolysaccharide (LPS) from Francisella tularensis (ATCC 29684) was analysed using NMR, mass spectrometry and chemical methods. The LPS contains a β‐GlcN‐(1–6)‐GlcN lipid A backbone, but has a number of unusual structural features; it apparently has no substituent at O‐1 of the reducing end GlcN residue in the lipid part in the major part of the population, no substituents at O‐3 and O‐4 of β‐GlcN, and no substituent at O‐4 of the Kdo residue. The largest oligosaccharide, isolated after strong alkaline deacylation of NaBH4 reduced LPS had the following structure: where Δ‐GalNA‐(1–3)‐β‐QuiNAc represents a modified fragment of the O‐chain repeating unit. Two shorter oligosaccharides lacking the O‐chain fragment were also identified. A minor amount of the disaccharide β‐GlcN‐(1–6)‐α‐GlcN‐1‐P was isolated from the same reaction mixture, indicating the presence of free lipid A, unsubstituted by Kdo and with phosphate at the reducing end. The lipid A, isolated from the products of mild acid hydrolysis, had the structure 2‐N‐(3‐O‐acyl4‐acyl2)‐β‐GlcN‐(1–6)‐2‐N‐acyl1−3‐O‐acyl3‐GlcN where acyl1, acyl2 and acyl3 are 3‐hydroxyhexadecanoic or 3‐hydroxyoctadecanoic acids, acyl4 is tetradecanoic or (minor) hexadecanoic acids. No phosphate substituents were found in this compound. OH‐1 of the reducing end glucosamine, and OH‐3 and OH‐4 of the nonreducing end glucosamine residues were not substituted. LPS of F. tularensis exhibits unusual biological properties, including low endoxicity, which may be related to its unusual lipid A structure.