title: Phosphorylated seryl and threonyl, but not tyrosyl, residues are efficient specificity determinants for GSK-3beta and Shaggy.
abstract: Glycogen synthase kinase-3 is involved in diverse functions including insulin signalling and development. In a number of substrates, phosphorylation by glycogen synthase kinase-3 is known to require prior phosphorylation at a Ser in the +4 position relative to its own phosphorylation site. Here we have used synthetic peptides derived from a putative glycogen synthase kinase-3 site in the Drosophila translation initiation factor eIF2B epsilon to investigate the efficacy of residues other than Ser(P) as priming residues for glycogen synthase kinase-3beta and its Drosophila homologue Shaggy. Glycogen synthase kinase-3beta phosphorylated peptides with Ser(P) and Thr(P) in the priming position, but peptides with Tyr(P), Thr, Glu or Asp were not phosphorylated. The Vmax for the Thr(P) peptide was three times higher than that of the Ser(P) peptide. These data suggest that glycogen synthase kinase-3 is unique among phosphate-directed kinases. The priming site specificity of Shaggy is similar to that of mammalian glycogen synthase kinase-3beta. This unpredicted efficacy of Thr(P) in the priming position suggests that there may be other unidentified substrates for these kinases.
authors.affiliation: Department of Anatomy and Physiology, University of Dundee, UK.
authors.forename: D D
authors.initials: DD
authors.lastname: Williams
authors.forename: O
authors.initials: O
authors.lastname: Marin
authors.forename: L A
authors.initials: LA
authors.lastname: Pinna
authors.forename: C G
authors.initials: CG
authors.lastname: Proud
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004330:Drosophila / Q000201:enzymology; D029721:Drosophila Proteins; D020717:Eukaryotic Initiation Factor-2B; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D020662:Guanine Nucleotide Exchange Factors; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000138:chemical synthesis / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D020717:Eukaryotic Initiation Factor-2B; D020662:Guanine Nucleotide Exchange Factors; D010455:Peptides; D011506:Proteins; D013912:Threonine; D014443:Tyrosine; D012694:Serine; D038341:Glycogen Synthase Kinases; D017346:Protein Serine-Threonine Kinases; C080335:Sgg protein, Drosophila; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3