FIGURE 5.

Dependence of the rate constant of the observable slow fluorescence change (k_obs) on the relative fluorescence amplitude. The relative amplitude of the total fluorescence change (ΔF/ΔF_(4.6)) was obtained by normalizing the fluorescence changes induced by the different [Ca²⁺] to that induced by pCa 4.6 (ΔF_(4.6)) in the particular experiment. k_obs-(ΔF/ΔF_(4.6)) obtained at the same [Ca²⁺]s were plotted as mean ± SE (circles and error bars). The solid line represents the k_obs-(ΔF/ΔF_(4.6)) dependence given by Eq. 1 according to the two-state model using the parameter means k_off = 36 s⁻¹ and k_on(app.4.6) = 326 s⁻¹, which were obtained from the six individual fits to the six experiments (see text). The solid line represents the dependence according to the three-state model to additionally specify the parameters for Ca²⁺ binding and dissociation (for details, see text).