Figure 1.
Inability of Prk1p to phosphorylate serine in its recognition motif. (A) Western blotting of Prk1p and its kinase-dead mutant Prk1D158Yp (Zeng and Cai, 1999). The HA-tagged proteins were immunoprecipitated from equal amounts of cell extracts with the rabbit anti-HA antibody and analyzed on immunoblots. (B) Prk1p was unable to phosphorylate LxxQxSG. The immunoprecipitated proteins and substrates used in each reaction are as indicated. Phosphorylation results were shown as autoradiography, and the input substrates were visualized by Coomassie Blue staining. The amino acid sequence of the 15th LxxQxTG motif of Pan1p (R15-WT) is shown on the top with each residue labeled according to their position relative to the phosphorylation target T.