Figure 3.

Effects of PLN and SLN on ATP-dependent Ca²⁺ translocation by SERCA. Normalized charges related to ATP concentration jumps on proteoliposomes containing SERCA, SERCA + PLN, or SERCA + SLN in the presence of 1 mm MgCl₂ (A) and 5 mm MgCl₂ (B) are shown. Free Ca²⁺ concentrations used were 10 (black columns; control measurement), 3 (white columns), and 0.3 μm (gray columns). Values are normalized with respect to the charge obtained following a 100 μm ATP jump in the presence of 10 μm free Ca²⁺. Error bars represent S.E. of at least four independent measurements. *, p < 0.01 compared with SERCA alone in A. **, p < 0.01 compared with SERCA alone in A but not significantly different when compare with each other. NS, not significant compared with SERCA alone in A.