FIG. 2.

eRF1 is phosphorylated by CK2 protein kinase in vivo. (A) Metabolic labeling of eRF1 in wild-type strain YDH6 (WT) or the CK2 temperature-sensitive mutant YDH8 (TS). Western blot data (WB) to determine steady-state protein levels and [³²P]orthophosphate metabolic labeling (³²P) were used to generate the ratios of ³²P incorporated per unit of eRF1 protein shown in B. Twenty-five micrograms of total protein was loaded into each lane for each Western blot, while 2.5 A₆₀₀ units of cells were immunoprecipitated with an eRF1-specific antiserum in each ³²P-labeling experiment. The data represent the mean values (± the standard deviation) of multiple experiments normalized to the wild-type strain grown at 25°C.