Plastocyanin

Plastocyanin is a copper-containing protein that mediates electron-transfer. It is found in a variety of plants, where it participates in photosynthesis. The protein is a prototype of the blue copper proteins, a family of intensely blue-colored metalloproteins. Specifically, it falls into the group of small type I blue copper proteins called "cupredoxins".

== Function == In photosynthesis, plastocyanin transfers an electron from the cytochrome f of the cytochrome b6f complex, to the P700+ from photosystem I. Cytochrome b6f complex and photosystem I are both membrane-bound proteins with residues exposed on the thylakoid lumen. Cytochrome f acts as an electron donor, while P700+ accepts electrons from reduced plastocyanin.