Campylobacter jejuni free oligosaccharides: function and fate

Area of Science:

• Microbiology
• Glycobiology
• Bacterial Pathogenesis

Background:

• Campylobacter jejuni utilizes an N-linked protein glycosylation pathway to modify periplasmic and membrane proteins with a heptasaccharide.
• A significant amount of this heptasaccharide is also released as a free oligosaccharide (fOS) into the periplasm, existing in higher quantities than its protein-linked form.

Purpose of the Study:

• To characterize the novel free oligosaccharide (fOS) component in Campylobacter jejuni.
• To investigate the bifunctional nature of the oligosaccharyltransferase PglB in cleaving fOS from its lipid anchor.
• To explore potential functions and regulatory mechanisms of fOS within the C. jejuni periplasm.

Main Methods:

• Structural analysis of the heptasaccharide in both free and protein-linked forms.
• Enzymatic assays to determine the activity of PglB on the undecaprenylpyrophosphate anchor.
• Comparative analysis of fOS levels under varying salt and osmolyte concentrations.

Main Results:

• The free oligosaccharide (fOS) is structurally identical to the N-linked heptasaccharide in C. jejuni.
• PglB, previously identified as an oligosaccharyltransferase, exhibits bifunctional activity, including hydrolase activity for fOS release.
• fOS levels are responsive to environmental changes in salt and osmolyte concentrations.

Conclusions:

• fOS is a novel, abundant soluble component in the C. jejuni periplasm.
• PglB plays a crucial role in both protein glycosylation and the release of fOS.
• Environmental factors can modulate fOS levels, suggesting a regulatory role for this molecule.