Plastocyanin/cytochrome c6 interchange in Scenedesmus vacuolatus

Plastocyanin and cytochrome c₆ from the green alga Scenedesmus vacuolatus were immunoquantified in cells grown under different concentrations of copper and iron. Plastocyanin expression was constitutive, its synthesis was not significantly affected by iron availability, and increases with copper availability. On the contrary, cytochrome c₆ synthesis is repressed by copper, and only residual amounts of the protein were detected at 0.1 μmol/L copper. Under copper deficiency, cytochrome c₆ is slightly dependent on iron. In natural environments, plastocyanin seems to be the predominant electron donor to P700.