• Prosthetic group features
• Plant­type ferredoxins in motif databases
• Plant­type ferredoxins in alignment databases
• Plant­type ferredoxins in 3­D databases
• References

Iron-sulphur cluster	Formal oxidation/spin states
[Fe2S2](SCys)4	[Fe2S2]+ (S=1/2); [Fe2S2]2+ (S=0)

Ferredoxins [1, 2] are iron-sulphur proteins that mediate electron transfer in a range of metabolic reactions; they fall into several subgroups according to the nature of their iron-sulphur cluster(s). One group, originally found in chloroplast membranes, has been termed "chloroplast­type" or "plant­type". Here, the active centre is a [Fe₂S₂] cluster, where the irons are tetrahedrally coordinated both by inorganic sulphurs and by sulphurs provided by four conserved Cys residues [3].

In chloroplasts, Fe₂S₂ ferredoxins function as electron carriers in the photosynthetic electron transport chain and as electron donors to various cellular proteins, such as glutamate synthase [4], nitrate reductase [5] and sulphite reductase [6]. In hydroxylating bacterial dioxygenase systems, they serve as intermediate electron­transfer carriers between reductase flavoproteins and oxygenase [2].

Several oxidoreductases contain redox domains similar to Fe₂S₂ ferredoxins, including ferredoxin / ferredoxin reductase components of several bacterial aromatic di­ and monooxygenases, cytoplasmic Fe hydrogenases, phenol hydroxylase, methane monooxygenase, vanillate demethylase oxidoreductase, phthalate dioxygenase reductase, bacterial fumarate reductase iron-sulphur protein, eukaryotic succinate dehydrogenase and xanthine dehydrogenase.

3­D structures are known for a number of Fe₂S₂ ferredoxins [3] and for the ferredoxin reductase / ferredoxin fusion protein phthalate dioxygenase reductase [7]. The fold belongs to the +ß class, with 1-3 ­helices and 3-5 ß­strands forming a barrel­like structure, and an extruded loop containing three of the four cysteinyl residues of the iron-sulphur cluster (Figure 1FRR):

                       I    II III 
                     ,-C----C--C---.
                     |  \   | /     \
                     |   [Fe2S2]     |
                  +H3N      \        |
                         ,--C--.    /
                         | IV  `---'
                  ¯OOC---'     

Plant­type ferredoxins in motif databases

PRINTS ID	PRINTS AC	PROSITE/BLOCKS ID	PROSITE AC	BLOCKS AC
2FE2SFRDOXIN	PR00159	2FE2S_FERREDOXIN	PS00197	BL00197

Plant­type ferredoxins in alignment databases

Protein Superfamily	Protein Homology Domain	Pfam	LPFC 3­D alignment
00028; Clostridium ferredoxin [2Fe-2S] 00029; ferredoxin [2Fe-2S] 00101; fumarate reductase Fe-S protein 00191; toluene dioxygenase ferredoxin component 81421; (phthalate dioxygenase reductase)	00254; ferredoxin [2Fe-2S]	PF00111; fer2	fer2

Plant­type ferredoxins in 3­D databases

PDB	scop	BSM	RELI Base	Header	¹
1a70	-	1a70	-	Ferredoxin (E92K mutant); spinach (recombinant form expressed in Escherichia coli	-
1awd	1awd	1awd	1awd	Ferredoxin (oxidised); Chlorella fusca	-
1doi	1doi	1doi	1doi	Ferredoxin; Haloarcula marismortui	MS7RL5
1dox	1dox	1dox	1dox	Ferredoxin; Synechocystis sp.	-
1doy	1doy	1doy	1doy	Ferredoxin; Synechocystis sp.	-
1frd	1frd	1frd	1frd	Heterocyst ferredoxin (oxidised, recombinant form); Anabaena sp. strain 7120	-
1frr	1frr	1frr	1frr	Ferredoxin I; Equisetum arvense	MS5WH2
1fxa	1fxa	1fxa	1fxa	Ferredoxin; Anabaena sp. strain PCC7120	-
1fxi	1fxi	1fxi	1fxi	Ferredoxin I; Aphanothece sacrum	MMS91042
1qoa	1qoa	1qoa	1qoa	Ferredoxin (C49S mutant); Anabaena sp. strain PCC7120	-
1qob	1qob	1qob	1qob	Ferredoxin (D62K mutant); Anabaena sp. strain PCC7120	-
1qoc	1qoc	1qoc	1qoc	Ferredoxin (D68K mutant); Anabaena sp. strain PCC7120	-
1qod	1qod	1qod	1qod	Ferredoxin (E94K mutant); Anabaena sp. strain PCC7120	-
1qoe	1qoe	1qoe	1qoe	Ferredoxin (E95K mutant); Anabaena sp. strain PCC7120	-
1qof	1qof	1qof	1qof	Ferredoxin (Q70K mutant); Anabaena sp. strain PCC7120	-
1qog	1qog	1qog	1qog	Ferredoxin (S47A mutant); Anabaena sp. strain PCC7120	-
1roe	1roe	1roe	1roe	Ferredoxin; Synechococcus elongatus	MS7KSC25
2cjn*	1cjn*	2cjn*	2cjn*	Ferredoxin; Synechococcus elongatus	-
2cjo*	1cjo*	2cjo*	2cjo*	Ferredoxin; Synechococcus elongatus	-
2pia	2pia	2pia	2pia	Phthalate dioxygenase reductase; Pseudomonas cepacia	MMS93161
4fxc	4fxc	4fxc	4fxc	Ferredoxin; Spirulina platensis	-

¹ Macromolecular Structures abstract. Full text is available to BioMedNet Members

References

1. Otaka, E. and Ooi, T. (1989) Examination of protein sequence homologies: V. New perspectives on evolution between bacterial and chloroplast­type ferredoxins inferred from sequence evidence. J. Mol. Evol. 29, 246-254.
2. Mason, J.R. and Cammack, R. (1992) The electron­transport proteins of hydroxylating bacterial dioxygenases. Annu. Rev. Microbiol. 46, 277-305.
3. Rypniewski, W.R., Breiter, D.R., Benning, M.M., Wesenberg, G., Oh, B.­H., Markley, J.L., Rayment, I. and Holden, H.M. (1991) Crystallization and structure determination to 2.5­Å resolution of the oxidized [2Fe-2S] ferredoxin isolated from Anabaena 7120. Biochemistry 30, 4126-4131.
4. Hirasawa, M., Chang, K.T. and Knaff, D.B. (1991) The interaction of ferredoxin and glutamate synthase: cross­linking and immunological studies. Arch. Biochem. Biophys. 286, 171-177.
5. Privalle, L.S., Privalle, C.T., Leonardy, N.J. and Kamin, H. (1995) Interactions between spinach ferredoxin-nitrite reductase and its substrates. Evidence for the specificity of ferredoxin. J. Biol. Chem. 260, 14344-14350.
6. Krueger, R.J. and Siegel, L.M. (1982) Spinach siroheme enzymes: Isolation and characterization of ferredoxin-sulfite reductase and comparison of properties with ferredoxin-nitrite reductase. Biochemistry 21, 2892-2904.
7. Correll, C.C., Batie, C.J., Ballou, D.P. and Ludwig, M.L. (1992) Phthalate dioxygenase reductase: a modular structure for electron transfer from pyridine nucleotides to [2Fe-2S]. Science 258, 1604-1610.

Bibliography on structural studies of plant­type ferredoxins

Reviews on plant­type ferredoxins