FIGURE 8.

Dependences of the observed rates and the fractions of the fast and slow phases on [CO] for CO binding to isolated βTrp-63(E7) subunits. A, squares represent the observed fractions of the fast (open), middle (gray), and slow (dark) phases (f_fast, f_middle, f_slow, respectively) observed after laser photolysis of Trp(E7) βCO subunits (see Figs. 2 and 3) B, open circles represent the observed rate for the fast phase, k_fast. C, light gray circles and dark circles represent the rates for the middle, k_middle, and slow, k_slow, phases, respectively, measured after laser photolysis. The light gray diamonds represent the slow phase measured in stopped flow rapid mixing experiments with the equilibrium forms of Trp(E7) deoxy-β subunits. The black lines represent fits to the model described in Scheme 3 for the blocked and closed states, and the fitted parameters are listed in the text after Equation 13. The experiments were conducted in 100 mm sodium phosphate, pH 7, 20 °C.