Figure 8.

Comparison of rate constants for the His79-heme alkaline conformational transition of WT*K79H iso-1-Cytc obtained from gated ET experiments to k_obs for the same conformational transition obtained with pH jump stopped-flow measurements. k_b obtained from gated ET data is shown with filled red symbols. k_f is either obtained from fits to the data in Figure 6 [filled green symbols, denoted k_f(gated ET)] or as k_f = K_C(H79)_app×k_b [open cyan symbols, denoted k_f(amp)] using the amplitude data in Figure 4B to obtain K_C(H79)_app. k_obs(gated ET) (filled blue symbols) is the sum of k_b and k_f(gated ET) and k_obs(amp) (open pink symbols) is the sum of k_b and k_f(amp). Error bars for k_f(amp) are from standard propagation of the errors in k_b and K_C(H79)_app (Table S12 in the Supporting Information). Error bars for k_obs(gated ET), and k_obs(amp) are obtained from standard propagation of the errors in k_b and k_f(gated ET) or k_f(amp). k_obs data from pH jump experiments (solid and open black triangles for downward and upward pH jumps, respectively) are from reference 44. The solid black curve is a fit of the pH dependence of the k_obs data from pH jump experiments to the mechanism in Figure 2, albeit without the pK_H1 ionization.^44,45