Equisetum (horsetail) ferredoxin: characterization of the active centre and position of the four cysteine residues in this 2Fe-2S protein.

Analysis of the ferredoxin of the primitive vascular plant Equisetum indicates that the cysteine residue normally found at position 18 of plant-type ferredoxins is replaced by a valine, although the spectroscopic properties of the ferredoxins are unaffected. It is concluded that the iron--sulphur cluster in plant-type ferredoxins is attached to cysteine residues 39, 44, 47 and 77.