Figure 7.

Electron transfer from photosystem I to CF independently of soluble Fd and competition between soluble and fused Fd for electrons in the presence of FNR. (a) Electron transfer chains involved during catalysis by C (left), where electrons flow from photosystem I (PSI) through the soluble Fd pool to the P450, and CF (right), where electrons flow from photosystem I via the Fd domain fused to the P450. (b) Electron flow toward FNR/NADP⁺ vs CF in the presence of soluble Fd (left). When soluble Fd is absent (right), more electrons flow through the fused Fd domain of CF and consequently end up being used for hydroxylation of Tyr; i.e., intramolecular electron transfer is faster than transfer to FNR.