Identification of myosin II as a binding protein to the PH domain of protein kinase B

Myosin II was identified as a binding protein to the pleckstrin homology (P H) domain of protein kinase B (PKB) in CHO cell extract by using the glutat hione S-transferase-fusion protein as a probe. When myosin II purified from rabbit skeletal muscle was employed, myosin II was shown to bind almost ex clusively to the PH domain of PKB among the PH domain fusion proteins exami ned. The purified myosin II bound to the PH domain of PKB with a K-d value of 1.1 x 10(-7) M. Studies with a series of truncated molecules indicated t hat the whole structure of the PH domain is required for the binding of myo sin II, and the binding to the PH domain was inhibited by phosphatidylinosi tol 4,5-bisphosphate. These results suggest that myosin II is a specific bi nding protein to the PH domain of particular proteins including PKB. (C) 19 99 Academic Press.