Rkp1/Cpc2, a fission yeast RACK1 homolog, interacts with Pck2, a PKC homolog, and is involved in the regulation of pck2-mediated signaling process. The N-terminal region of split pleckstrin homology domain (nPH) in human PLC-gamma1 bound to Rkp1/Cpc2 concomitantly with Pck2. nPH inhibited kinase activity of GST-Pck2 purified from Schizosaccharomyces pombe in vitro. The lethality induced by pck2(+) overexpression was suppressed by coexpression of either rkp1(+) or nPH domain. This result suggests that Rkp1/Cpc2 interacts with PH domain-containing protein and regulates the Pck2-mediated signaling process in S. pombe.