Structural and mechanistic investigations of protein S-glycosyltransferases

Cell Chem Biol. 2021 Dec 16;28(12):1740-1749.e6. doi: 10.1016/j.chembiol.2021.06.009. Epub 2021 Jul 21.


Attachment of sugars to nitrogen and oxygen in peptides is ubiquitous in biology, but glycosylation of sulfur atoms has only been recently described. Here, we characterize two S-glycosyltransferases SunS and ThuS that selectively glycosylate one of five Cys residues in their substrate peptides; substitution of this Cys with Ser results in a strong decrease in glycosylation activity. Crystal structures of SunS and ThuS in complex with UDP-glucose or a derivative reveal an unusual architecture in which a glycosyltransferase type A (GTA) fold is decorated with additional domains to support homodimerization. Dimer formation creates an extended cavity for the substrate peptide, drawing functional analogy with O-glycosyltransferases involved in cell wall biosynthesis. This extended cavity contains a sharp bend that may explain the site selectivity of the glycosylation because the target Cys is in a Gly-rich stretch that can accommodate the bend. These studies establish a molecular framework for understanding the unusual S-glycosyltransferases.

Keywords: RiPPs; S-glycosylation; S-glycosyltransferase; antibiotic; bacteriocin; crystallography; glycocin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cystine / chemistry
  • Cystine / genetics
  • Cystine / metabolism
  • Glycosylation
  • Glycosyltransferases / chemistry
  • Glycosyltransferases / genetics
  • Glycosyltransferases / metabolism*
  • Protein Conformation


  • Cystine
  • Glycosyltransferases