Glycogen Synthase Kinase 3 (GSK‑3) is a serine/threonine protein kinase and one of several protein kinases, which phosphorylate glycogen synthase. It is also called Factor A (FA) for its ability to activate the MgATP-dependent form of the protein phosphatase PP1 called FC(1-4). Recent studies demonstrate that GSK-3 can autophosphorylate Ser, Thr and Tyr. Ser/Thr phosphorylation causes inactivation, and Tyr phosphorylation results in increased activity (Y216 for GSK-3β). GSK-3 expressed inE. colior insect cells is extensively phosphorylated on Tyr. Molecules lacking phosphate at this position can autophosphorylate after incubation with Mg2+and ATP. GSK-3 phosphorylates several exogenous substrates, but not on Tyr residues (5,6).
Protein serine/threonine kinase
Rabbit skeletal muscle, recombinant (E. coli)
Supplied with 10X Reaction Buffer
Product Source
Isolated from a strain ofE. colithat carries a clone expressing GSK-3β derived from a rabbit skeletal muscle cDNA library (kindly provided by Dr. P. J. Roach) (5).
Recognition Determinant
The substrate specificity of GSK-3 is unique and substrate dependent. For some substrates, prior phosphorylation of the substrate to form the motifS/TXXXpS/pT is a strict requirement whereas in other substrates, no previous phosphorylation is needed. In either case, many of the GSK-3 sites have Pro residues close to the modified Ser or Thr (5,7).