Figure 5.

Charge translocation as a function of calcium concentration for proteoliposomes under different starting conditions. A, proteoliposomes containing SERCA alone. B, proteoliposomes containing SERCA and PLN. Normalized charges related to simultaneous ATP (100 μm) and free Ca²⁺ (various concentrations) jumps are indicated by circles and a black line. Values are normalized with respect to the charge obtained following a simultaneous 100 μm ATP and 10 μm free Ca²⁺ jump. Normalized charges related to free Ca²⁺ (various concentrations) jumps in the presence of 100 μm ATP are indicated by triangles and a gray line. Values are normalized with respect to the charge obtained following a 10 μm free Ca²⁺ jump in the presence of 100 μm ATP. Normalized charges related to ATP jumps in the presence of various Ca²⁺ concentrations are indicated by squares and a gray dashed line. Values are normalized with respect to the charge obtained following a 100 μm ATP jump in the presence of 10 μm free Ca²⁺. The lines represent curve fitting of the experimental data using the Hill equation (kinetic parameters can be found in Table 1). Error bars represent S.E. of at least four independent measurements.