Figure 1. Reaction cycle and dose–response of turnover rate to cytosolic and luminal Ca²⁺ in SERCA2b model.

(A) Reaction cycle of SERCA. Clockwise direction of a reaction in the cycle is defined as a ‘forward’ reaction. The numbers shown with the reactions are used in the text in order to refer to individual reactions. (B1) Estimated dose–response of the turnover rate of SERCA2b against [Ca²⁺]_c and [Ca²⁺]_ER. Note that [Ca²⁺]_c is expressed on a logarithmic scale and [Ca²⁺]_ER is on a linear scale (this representation is chosen for visual convenience). (B2) Turnover rate at different [Ca²⁺]_ER when [Ca²⁺]_c=1 μM. (B3) Turnover rate at different [Ca²⁺]_c when [Ca²⁺]_ER=10 μM.