| Modification Notes |
Two serine/threonine kinases, designated Akt1 and Akt2 (alternatively referred to as PKB or RacPK), exhibit sequence homology with the protein kinase A and C families and are encoded by the c-akt proto-oncogene. Akt1 and Akt2 contain a pleckstrin homology domain (PH) and are activated by PDGF stimulation. This activation is dependent on PDGFR-∫ tyrosine residues 740 and 751, which bind a subunit of the phosphatidylinositol 3-kinase (PI 3-kinase) complex. Additionally, the activation of Akt1 and Akt2 is inhibited by the PI kinase inhibitor wortmannin. Taken together, these data strongly suggests that the protein signals downstream of the PI kinases. PKB kinase (for protein kinase B kinase) has also been identified as a primary signal transducer that enables the activation of Akt by the PI 3-kinase complex. Phosphorylation of Ser-241 is essential for PKB Kinase activity, unlike its other phosphorylation sites. PKB Kinase can phosphorylate itself at Ser-241, leading to its own activation. |