Figure 7.

(A) Comparison of the reaction sequences in the wild-type (white boxes) and ML(II-263) (gray boxes) enzymes. For simplicity, the states of the binuclear center are indicated with the corresponding O₂ intermediates P_R, F, and O. The energy scale of the ordinate is arbitrary, except the free-energy difference between states (3) and (3*) of about 10² millielectronvolts (meV). This difference in the energy levels of states (3) and (3*) results in a different population sequence (in time) for the intermediates in the wild-type (B) and ML(II-263) (C) mutant enzymes. The curve for (3*) in (C) is not shown because this intermediate is only populated to a maximum of about 2%.