Crystal structure determination at 1.4 A resolution of ferredoxin from the green alga Chlorella fusca.
BACKGROUND
[2Fe-2S] ferredoxins, also called plant-type ferredoxins, are low-potential redox proteins that are widely distributed in biological systems. In photosynthesis, the plant-type ferredoxins function as the central molecule for distributing electrons from the photolysis of water to a number of ferredox-independent enzymes, as well as to cyclic photophosphorylation electron transfer. This paper reports only the second structure of a [2Fe-2S] ferredoxin from a eukaryotic organism in its native form.


RESULTS
Ferredoxin from the green algae Chlorella fusca has been purified, characterised, crystallised and its structure determined to 1.4 A resolution - the highest resolution structure published to date for a plant-type ferredoxin. The structure has the general features of the plant-type ferredoxins already described, with conformational differences corresponding to regions of higher mobility. Immunological data indicate that a serine residue within the protein is partially phosphorylated. A slightly electropositive shift in the measured redox potential value, -325 mV, is observed in comparison with other ferredoxins.


CONCLUSIONS
This high-resolution structure provides a detailed picture of the hydrogen-bonding pattern around the [2Fe-2S] cluster of a plant-type ferredoxin; for the first time, it was possible to obtain reliable error estimates for the geometrical parameters. The presence of phosphoserine in the protein indicates a possible mechanism for the regulation of the distribution of reducing power from the photosynthetic electron-transfer chain.
Bes
M T
MT
Institut für Anorganische Chemie der Universität Göttingen, Tammannstrasse 4, 37077, Göttingen, Germany.
Parisini
E
E
Inda
L A
LA
Saraiva
L M
LM
Peleato
M L
ML
Sheldrick
G M
GM
D000595:Amino Acid Sequence; D002708:Chlorella / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D007526:Isoelectric Point; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010768:Phosphoserine / Q000737:chemistry; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D005288:Ferredoxins; D010768:Phosphoserine