The pleckstrin homology domain of RAC protein kinase associates with the regulatory domain of protein kinase C zeta.

Binding proteins to the pleckstrin homology domain of RAC protein kinase were screened by using glutathione S-transferase fusion protein system. Proteins in CHO cell extract of approximate molecular mass of 76 kD and 200 kD bound specifically to the pleckstrin homology domain of RAC protein kinase in vitro. The 76 kD protein was identified as protein kinase C zeta by immunoblot analysis. Studies of the association between the pleckstrin homology domain-truncated mutants and protein kinase C zeta indicated that the amino-terminal portion of the pleckstrin homology domain is essential for the binding and the whole structure of the domain is important for the efficient binding to protein kinase C zeta. The pleckstrin homology domain of RAC protein kinase was shown to recognize the regulatory domain of protein kinase C zeta. The protein-protein interaction between RAC protein kinase and protein kinase C through the pleckstrin homology domain might be important for the regulation of these protein kinases.