Purified by affinity chromatography. GSK-3 is one of the Akt substrates. It can be phosphorylated by Akt at Ser21 of GSK-3a or Ser9 of GSK-3b. The phosphorylation of GSK negatively regulates its kinase activity. The recombinant GSK-3a fusion protein serves as a useful substrate for assaying Akt kinase activity. Product Description: E. coli-expressed recombinant fusion protein of GSK-3alpha residues (amino acids 12-30, UniProt accession #P49840) surrounding GSK-3a Ser21 and Glutathione S-transferase (GST). Activity: GSK-3a fusion protein at a concentration of 2ug/20ul reaction was phosphorylated in an in vitro kinase assay with 200 mM ATP. After 30 minutes incubation at 30°C, phosphorylation was detected by Western blot with phospho-speci?c GSK-3a antibodies.