Figure 2.

The slow phase of k_AB⁽²⁾ as a function of CdSO₄ concentration for native (●), and mutant DN(M17) (■) and DN(L210) (○) RCs. In native RCs, k_AB⁽²⁾ is independent of CdSO₄ concentration above 10 μM. In mutant RCs, k_AB⁽²⁾ displays a sigmoidal dependence on CdSO₄ concentration. The solid curve represents a theoretical fit using the kinetic model described by Eq. 5 (see also Eq. A4 of Appendix) with the parameters shown in Table 2. The drastic difference in behavior between native and mutant RCs is because of the lack of competition of k_off with k_AB⁽²⁾(Cd²⁺) in native RCs (see Discussion). Conditions: same as in Fig. 1.