Ferredoxin, which can be isolated from spinach leaves, contains a 2Fe2S cluster. It is an important part of the photosystem and is responsible for the electron transfer to reduce quinone. It is located in the membrane of the photosynthetic system and is located near manganese clusters and the quinone units.
Two iron atoms are connected by two sulfur atoms. The coordination sphere is completed by cysteinato ligands from the protein side chain.