FIGURE 3.

Ca²⁺-ATPase activities of expressed SERCA1a. The Ca²⁺-ATPase activity of microsomes expressing the wild-type or mutant SERCA1a was determined with 0.1 mm [γ-³²P]ATP as described under “Experimental Procedures.” The activities are divided by the amount of EP formed at steady state (see supplemental Fig. S1), and the turnover rates thus obtained are shown as percentage of that of the wild type (7.29 ± 0.42 s⁻¹ (n = 5)). The values of the mutants presented are the mean ± S.D. (n = 3–5).