Defined Glycan Ligands for Detecting Rare l-Sugar-Binding Proteins

Area of Science:

• Glycoscience
• Microbiology
• Immunology

Background:

• Cell surfaces feature diverse sugar structures recognized by carbohydrate-binding proteins (CBPs).
• Bacteria synthesize numerous rare sugars absent in mammals, potentially mediating host-pathogen interactions.
• Limited tools exist to identify CBPs for these rare sugars.

Purpose of the Study:

• To develop chemoenzymatic strategies for synthesizing glycoconjugates containing rare l-sugars.
• To investigate the substrate specificity of bacterial and mammalian glycosyltransferases (GTs) for rare sugars.
• To identify novel rare sugar-binding proteins in human serum.

Main Methods:

• Chemoenzymatic synthesis of l-colitose (l-Col) and other activated l-sugars.
• Glycosylation reactions using bacterial and mammalian GTs with various glycan acceptors.
• Confirmation of sugar incorporation using known CBPs.
• Detection of rare sugar-binding proteins in human serum.

Main Results:

• Successful synthesis of l-Col and activated l-sugars.
• Demonstrated that bacterial and mammalian GTs can transfer l-Col, l-fucose (l-Fuc), and l-galactose (l-Gal) onto different glycan acceptors.
• Confirmed incorporation of these l-sugars into glycoconjugates.
• Identified rare sugar-binding proteins in human serum.

Conclusions:

• Bacterial and mammalian GTs exhibit similar substrate specificities, enabling in vitro glycoconjugate construction.
• This work provides tools to unveil novel mediators of host-pathogen interactions by detecting rare sugar-binding proteins.
• The developed methods facilitate the study of microbial glycans and their recognition by the host immune system.