Figure 4.

pH rate profiles for NH₂Y• formation in the reactions of NH₂Y₇₃₀-α2 (blue dots) or NH₂Y₇₃₁-α2 (red dots) with F₃Y₃₅₆-β2 in the presence of CDP/ATP. pH dependence of the rate constants from the 1^st (A), 2^nd (B) and 3^rd (C) kinetic phases determined from the tri-exponential fits (Table 1). In (D), the data from panel (C) are overlaid with the pH rate profiles for [¹⁴C]-dCDP formation with F₃Y₃₅₆-β2/wt α2 (black dots) and with intein wt-β2/wt α2 (green squares), determined in a previous study (18).