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Structural Biology and Analytical Chemistry Approaches for Characterizing C-Glycoside Metabolic Enzymes in Human Gut Microbiota
Published on: May 23, 2025
Glycopeptide specificity of the secretory protein folding sensor UDP-glucose glycoprotein:glucosyltransferase
Sean C Taylor1, Pierre Thibault, Daniel C Tessier
1Biochemistry Department, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
Abstract:
Secretory and membrane N-linked glycoproteins undergo folding and oligomeric assembly in the endoplasmic reticulum with the aid of a folding mechanism known as the calnexin cycle. UDP-glucose glycoprotein:glucosyltransferase (UGGT) is the sensor component of the calnexin cycle, which recognizes these glycoproteins when they are incompletely folded, and transfers a glucose residue from UDP-glucose to N-linked Man9-GlcNAc2 glycans. To determine how UGGT recognizes incompletely folded glycoproteins, we used purified enzyme to glucosylate a set of Man9-GlcNAc2 glycopeptide substrates in vitro, and determined quantitatively the glucose incorporation into each glycan by mass spectrometry. A ranked order of glycopeptide specificity was found that provides the criteria for the recognition of substrates by UGGT. The preference for amino-acid residues close to N-linked glycans provides criteria for the recognition of glycopeptide substrates by UGGT.
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