PDPK1 (PDK1) activates ribosomal S6 kinases (RSKs) by phosphorylating a conserved serine residue S221 (in RPS6KA1). The binding site for PDPK1 on RSKs is available after RSK phosphorylation by MAPKs/ERKs. PDPK1 is present in the activated form at the plasma membrane where the phosphorylation occurs (Jensen et al. 1999).
protein serine/threonine kinase activity of PDPK1:PIP3,PDPK1:PIP2 [plasma membrane]