Cytochrome f /Plastocyanin Complex

Abstract In the photosynthetic electron transfer chain in plants, cytochromef, a subunit of the cytochromeb6fcomplex, acts as electron donor for plastocyanin. Plastocyanin is a small soluble protein, which shuttles electrons to photosystem 1. The structure of the short‐lived and weak complex of the soluble domain of cytochromefand plastocyanin has been determined using nuclear magnetic resonance. It shows that the heme iron of cytochromefand the copper ion of plastocyanin are in close proximity, enabling fast electron transfer. The copper ligand His87 is located close to the iron ligand Tyr1, suggesting that electron transfer occurs via the hydrophobic patch of plastocyanin. Electrostatic interactions are also important in the complex. These findings are discussed in the light of studies of the electron transfer kinetics.