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Structural studies on the glucose-heptose region of the Proteus mirabilis R core
Abstract:
Methylation analysis of the core oligosaccharide of the Proteus mirabilis mutant R4 (derived from serotype 028 was carried out in order to obtain information on the internal (glucose-heptose) region of the P. mirabilis R core. The isolated core oligosaccharide was composed of glucose, L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid (dOclA) and phosphorus in a molar ratio of about 1:2:1:1.4. It was methylated either directly or after dephosphorylation. To localize the position of the phosphate substituents, the permethylated product was dephosphorylated with hydrogen fluoride and the oligosaccharide obtained was remethylated using C2H3I. Location of phosphate at C-7 of the terminal heptose was shown by isolation of the sugar phosphate from partial hydrolysates and gas-liquid chromatography/mass spectrometry of the permethylated product. Combining the data of the methylation analysis with the data of an NMR study allows one to formulate the structure of the core oligosaccharide as folllows: (formula: see text).
Insights
Methylation analysis elucidated the core oligosaccharide structure of Proteus mirabilis mutant R4. Phosphate was located at the C-7 position of the terminal heptose sugar.
Area of Science:
- Microbiology
- Carbohydrate Chemistry
- Structural Biology
Background:
- Proteus mirabilis is an opportunistic pathogen.
- Understanding its lipopolysaccharide (LPS) core structure is crucial for vaccine development and pathogenesis studies.
- Mutant R4 provides a model for studying the P. mirabilis R core structure.
Purpose of the Study:
- To determine the internal (glucose-heptose) region of the P. mirabilis R core oligosaccharide.
- To localize the position of phosphate substituents within the core oligosaccharide.
Main Methods:
- Methylation analysis of the isolated core oligosaccharide.
- Dephosphorylation and remethylation strategies to identify phosphate positions.
- Gas-liquid chromatography/mass spectrometry (GLC-MS) for structural elucidation.
- Nuclear Magnetic Resonance (NMR) spectroscopy.
Main Results:
- The core oligosaccharide consists of glucose, L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid (KDO), and phosphorus in a molar ratio of approximately 1:2:1:1.4.
- Phosphate substituents were localized to the C-7 position of the terminal heptose.
- The complete structure of the core oligosaccharide was proposed based on combined methylation and NMR data.
Conclusions:
- The study successfully elucidated the structure of the P. mirabilis R core oligosaccharide, including the precise location of phosphate groups.
- This detailed structural information is vital for understanding P. mirabilis biology and for potential therapeutic interventions.