FIG. 1.

Detection of protein kinase activity in the membrane fraction of S. solfataricus. Shown are the results of an in gel assay of S. solfataricus protein kinase activity following SDS-PAGE. Portions, containing 20 μg of total protein each, of the cytosolic fraction (C) and the detergent extract of the membrane fraction (M) from S. solfataricus were electrophoresed into an SDS–10% (wt/vol) polyacrylamide gel in which either BSA or casein had been copolymerized into the gel matrix at a concentration of 1 mg/ml. Following electrophoresis, the gel was washed free of SDS and the proteins within it were renatured using guanidine hydrochloride. The gels were each then incubated for 60 min in 30 ml of 20 mM MES, pH 6.5, containing 0.5 mM EDTA, 5 mM Mg²⁺, 5 mM Mn²⁺, and 50 μM [γ-³²P]ATP (specific activity, 30 Ci/mol). The gels then were washed to remove free ATP, and regions of each gel in which [³²P]phosphate was incorporated into protein were visualized by autoradiography using X-ray film. Shown are the autoradiograms of each gel. The positions and molecular masses (in kilodaltons) of the protein standards are indicated at the left.