FIGURE 2.

TNP-8N₃-ATP (left panels) and ATP (right panels) concentration dependences of photolabeling of wild type Ca²⁺-ATPase stabilized in the intermediate states occurring during E2P dephosphorylation. Expressed wild type Ca²⁺-ATPase (upper panels) or SR (lower panels) was incubated with Tg, MgF, vanadate, AlF, or BeF as described under “Experimental Procedures,” and subjected to TNP-8N₃-ATP photolabeling at the indicated concentrations of TNP-8N₃-ATP without ATP (left panels), or at 3× the K_0.5 for TNP-8N₃-ATP with the indicated concentrations of ATP (right panels). In each case, the maximum level of specific labeling was defined as 100%. Symbols for all panels are indicated in the upper left panel.