Figure 5.

Effect of ouabain on the phosphorylation capacity of the chimeras and wild-type H⁺,K⁺-ATPase. Sf9 membranes were preincubated as in Fig. 4, using varying concentrations of ouabain. After phosphorylation at 21°C for 10 s with 0.1 μM [γ-³²P]ATP, the phosphorylation level (EP) was determined and corrected for that of the mock. The phosphorylation level of H⁺,K⁺-ATPase in the absence of ouabain was set at 100%. ■, H⁺,K⁺-ATPase; □, HNN3; ●, HN36; ○, HN34; ▴, HN56; ▿, HN34/56. Shown is the average of two enzyme preparations.