Multisite phosphorylation of the glycogen-binding subunit of protein phosphatase-1G by cyclic AMP-dependent protein kinase and glycogen synthase kinase-3.
The glycogen-binding (G) subunit of protein phosphatase-1G is phosphorylated stoichiometrically by glycogen synthase kinase-3 (GSK3), and with a greater catalytic efficiency than glycogen synthase, but only after prior phosphorylation by cyclic AMP-dependent protein kinase (A-kinase) at site 1. The residues phosphorylated are the first two serines in the sequence AIFKPGFSPQPSRRGS-, while the C-terminal serine (site 1) is one of the two residues phosphorylated by A-kinase. These findings demonstrate that (i) the G subunit undergoes multisite phosphorylation in vitro; (ii) phosphorylation by GSK3 requires the presence of a C-terminal phosphoserine residue; (iii) GSK3 can synergise with protein kinases other than casein kinase-2.
Dent
P
P
Department of Biochemistry, Medical Sciences Institute, University of Dundee, Scotland.
Campbell
D G
DG
Hubbard
M J
MJ
Cohen
P
P
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites / Q000187:drug effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002918:Chymotrypsin; D006003:Glycogen / Q000032:analysis*; D006006:Glycogen Synthase / Q000378:metabolism; D038341:Glycogen Synthase Kinases; D007525:Isoelectric Focusing; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000032:analysis; D010749:Phosphoprotein Phosphatases / Q000032:analysis*; D010766:Phosphorylation; D011494:Protein Kinases / Q000494:pharmacology*; D012694:Serine / Q000032:analysis; D013379:Substrate Specificity; D014357:Trypsin
D000596:Amino Acids; D010748:Phosphopeptides; D012694:Serine; D006003:Glycogen; D006006:Glycogen Synthase; D011494:Protein Kinases; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D002918:Chymotrypsin; D014357:Trypsin