Fig. 2

The Ca²⁺-ATPase activity supported by oxalate was uncoupled by 1,2-DCB. The effect of 1,2-DCB on Ca²⁺/P_i coupling ratio was determined. The coupling ratio at each DCB concentration was calculated as the ratio between the Ca²⁺ uptake rate and the ATP hydrolysis rate by SERCA. SR vesicles (0.01 mg/ml) were equilibrated at 25 °C in a medium containing 5 mM K-oxalate. Hydrolysis rate of ATP (a) or ⁴⁵Ca²⁺ uptake rates (b) were measured at same experimental conditions. c The Ca²⁺/P_i coupling ratio (calculated by dividing the Ca²⁺ transport values by those of ATP hydrolysis), in presence of different concentrations of 1,2-DCB was uncoupled