Figure 8.
Modified four-state kinetic model for cytochrome c reduction by dual-flavin enzymes. The model indicates a sequential cycling among conformationally open or closed forms that contain FMN semiquinone or FMN hydroquinone. Rates of conformational opening (k−1 and k−3) and closing (k1 and k3), FMN reduction (k2), and the rates of ET to oxidized cytochrome c (k4 and k4′) are indicated. Ksq and Khq are the conformational equilibrium settings for the partly oxidized and fully reduced forms of the enzyme, respectively. We assumed Ksq = Khq = Keq in our study. FNR is the NADPH/FAD domain. See text for details.