Ferredoxin reductase (FNR) catalyses the final electron transport step of linear photosynthesis, receiving one electron from two electron carrier ferredoxin proteins and uses these electrons to convert NADP+ into NADPH via hydride transfer from atom N(5) of the FAD cofactor using two molecules of ferredoxin (Fd) as the source of the electrons.
In chloroplasts and cyanobacteria the enzyme acts on plant-type [2Fe-2S] ferredoxins, but in other bacteria it can also reduce bacterial 2[4Fe-4S] ferredoxins and flavodoxin.
FNR is a member of a large family of electron transport proteins containing NAD and FAD binding sites which form an FNR-like module.
Defined by 5 residues: TYR:A-95SER:A-96CYS:A-272GLU:A-312TYR:A-314