One group of ferredoxins, originally found in chloroplast membranes, has been termed "chloroplast-type" or "plant-type" (). Its active center is a [FeS] cluster, where the iron atoms are tetrahedrally coordinated both by inorganic sulfur atoms and by sulfurs of four conserved cysteine (Cys) residues.
In chloroplasts, FeS ferredoxins function as electron carriers in the photosynthetic electron transport chain and as electron donors to various cellular proteins, such as glutamate synthase, nitrite reductase, sulfite reductase, and the cyclase of chlorophyll biosynthesis. Since the cyclase is a ferredoxin dependent enzyme this may provide a mechanism for coordination between photosynthesis and the chloroplasts need for chlorophyll by linking chlorophyll biosynthesis to the photosynthetic electron transport chain. In hydroxylating bacterial dioxygenase systems, they serve as intermediate electron-transfer carriers between reductase flavoproteins and oxygenase.