Phosphoserine as a recognition determinant for glycogen synthase kinase-3: Phosphorylation of a synthetic peptide based on the G-component of protein phosphatase-1

Carol J. Fiol, Joseph H. Haseman, Yuhuan Wang, Peter J. Roach, Roger W. Roeske, Maria Kowalczuk, Anna A. DePaoli-Roach

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71 Scopus citations


Prior phosphorylation of its substrate has been shown to be important for substrate recognition by the protein kinase glycogen synthase kinase-3 (GSK-3). Phosphorylation of glycogen synthase by GSK-3 is known to be enhanced by the previous action of casein kinase II and the sequence -SXXXS(P)- was proposed as the minimal recognition determinant for GSK-3. The glycogen binding subunit of type 1 phosphoprotein phosphatase has been shown to be phosphorylated by cyclic AMP-dependent protein kinase at serine-13 in the sequence KPGFS(5)PQPS(9)RRGS(13)ESSEEVYV (F. B. Caudwell, A. Hiraga, and P. Cohen (1986) FEBS Lett. 194, 85-89). Inspection of the sequence revealed potential GSK-3 sites at residues 5 and 9. Using a synthetic peptide with the above sequence, we found that phosphorylation of serine-13 by cyclic AMP-dependent protein kinase permitted the recognition of serine-9 and serine-5 by GSK-3. The work provides another example of a substrate for GSK-3 and demonstrates that the action of GSK-3 is linked to the presence of phosphate in the substrate and not the action of any particular protein kinase. In the course of the analyses, a novel feature of trypsin cleavage of phosphopeptides was noted. In the sequence -SRRGS(P)- trypsin acted uniquely after the first arginine whereas in the sequence -S(P)RRGS(P)- it cleaved randomly at either arginine residue. The fact that GSK-3 could phosphorylate a peptide derived from a phosphatase subunit also raises the possibility that GSK-3 might be involved in controlling glycogenassociated type 1 phosphatase and, more generally, in mediating cyclic AMP control of protein phosphorylation in cells.

Original languageEnglish (US)
Pages (from-to)797-802
Number of pages6
JournalArchives of Biochemistry and Biophysics
Issue number2
StatePublished - Dec 1988


ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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