FIG. 3.

Kinase activity of HGK mutants in RIE-1 cells. HGK wild-type and mutant proteins were immunoprecipitated from stable pools of RIE-1 cells infected with HGK retroviruses. (A) Comparison of the T187E and T191E activation loop mutations with wild-type kinase. The top panel shows an autoradiogram of samples analyzed by SDS-PAGE, showing the relative amount of ³²P incorporated into myelin basic protein (MBP) after incubation of the immunoprecipitate and [γ-³²P]ATP for 20 min at 30^οC. The bottom panel shows the relative amount of HGK proteins in the immunoprecipitate. (B) Comparison of the T191E and K54R catalytically inactive HGK mutants with wild-type HGK. An autoradiogram shows the relative amount of ³²P incorporation both into HGK protein (autophosphorylation) and into added MBP in the immunoprecipitate.