FIGURE 6.
Effect of ATP on the conformation of the PMCA transmembrane domain. Specific incorporation of [125I]TID-PC/16 to PMCA was determined as a function of increasing ATP concentrations in the presence of 2 mm EGTA (A), 2 mm EGTA plus 50 μm (VO4)3− (B), or 100 μm free Ca2+ plus 50 μm (VO4)3− (C). The continuous lines are the graphs of Equation 2 for the best fitting parameter values shown in Table 1 (Reactions iv, v, and viii, respectively). D, the specific incorporation of [125I]TID-PC/16 to PMCA in media with 2 mm EGTA and 2 mm ATP did not vary with the concentration of (VO4)3− (continuous line), and thus Kx could not be experimentally determined (see Table 1, Reaction vii).