Glycopeptide specificity of the secretory protein folding sensor UDP-glucose glycoprotein:glucosyltransferase.
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.
Taylor
Sean C
SC
Biochemistry Department, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
Thibault
Pierre
P
Tessier
Daniel C
DC
Bergeron
John J M
JJ
Thomas
David Y
DY
D000595:Amino Acid Sequence; D000818:Animals; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006020:Glycopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D006023:Glycoproteins / Q000096:biosynthesis / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D017510:Protein Folding; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology
D006020:Glycopeptides; D006023:Glycoproteins; D011994:Recombinant Proteins; D005964:Glucosyltransferases; C072423:mannosylglycoprotein 1,3-glucosyltransferase