Rkp1/CPC2, a RACK1 Homolog, Interacts with Pck1 to Regulate PKC-Mediated Signaling in Schizosaccharomyces pombe

The Rkpl/CPC2, a receptor for activated protein kinase C of Schizosaccharomyces pombe, contains seven WD motifs found in the G-protein β-subunit. A 110-kDa protein was identified to interact with Rkp1/CPC2 by immunoprecipitation and following in vitro binding assay. To examine its kinase activity and binding ability to Rkp1, the pck1 , a PKC homolog of S. pombe, was cloned. Pckl phosphorylated myelin basic protein (MBP) and histone H1 in a phospholipid-dependent and Ca 2+ -independent manner. It was demonstrated that the N-terminal region of Pckl was responsible for the binding to Rkpl, thus suggesting that Rkpl interacted with Pckl to regulate Pckl-mediated signaling in S. pombe.