Reciprocal keratin 18 Ser48 O-GlcNAcylation and Ser52 phosphorylation using peptide analysis

Biochem Biophys Res Commun. 2006 Dec 22;351(3):708-12. doi: 10.1016/j.bbrc.2006.10.092. Epub 2006 Oct 27.


Phosphorylation and O-GlcNAcylation of keratin 18 (K18) are highly dynamic and involve primarily independent K18 populations. We used in vitro phosphorylation and O-GlcNAcylation of wild-type, phospho-Ser52, glyco-Ser48, and Ser-to-Ala mutant 17mer peptides (K18 amino acids 40-56), which include the major K18 glycosylation (Ser48) and phosphorylation (Ser52) sites, to address whether each modification blocks the other. The glyco-K18 peptide blocks Ser52 phosphorylation by protein kinase C, an in vivo K18 kinase, while the phospho-K18 peptide blocks its O-GlcNAcylation. Our findings support the reciprocity of these two post-translational modifications. Therefore, regulation of protein Ser/Thr phosphorylation and glycosylation at proximal sites can be interdependent and provides a potential mechanism of counter regulation.

Publication types

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

MeSH terms

  • Acylation
  • Amino Acid Substitution
  • Glycine / chemistry*
  • Keratin-18 / chemistry*
  • Peptides / chemistry
  • Phosphorylation
  • Serine / chemistry*
  • Structure-Activity Relationship


  • Keratin-18
  • Peptides
  • Serine
  • Glycine