Chloroplast monothiol glutaredoxins as scaffold proteins for the assembly and delivery of [2Fe-2S] clusters

• Published in: The EMBO journal Vol. 27; no. 7; pp. 1122 - 1133
• Main Authors: Bandyopadhyay, Sibali, Gama, Filipe, Molina-Navarro, Maria Micaela, Gualberto, José Manuel, Claxton, Ronald, Naik, Sunil G, Huynh, Boi Hanh, Herrero, Enrique, Jacquot, Jean Pierre, Johnson, Michael K, Rouhier, Nicolas
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 09.04.2008; Nature Publishing Group UK; Blackwell Publishing Ltd; EMBO Press; Nature Publishing Group
• Subjects: Amino Acid Sequence; Apoproteins - metabolism; Arabidopsis - enzymology; Arabidopsis Proteins; Binding Sites; Biochemistry, Molecular Biology; Botany; Cellular biology; chloroplast; Chloroplasts - enzymology; Circular Dichroism; Ferredoxins - metabolism; Flowers & plants; Gene expression; Genetic Complementation Test; glutaredoxin; Glutaredoxins - chemistry; Glutaredoxins - metabolism; Iron-Sulfur Proteins - isolation & purification; Iron-Sulfur Proteins - metabolism; iron-sulphur protein; Kinetics; Life Sciences; Models, Biological; Molecular Sequence Data; Mutation - genetics; plant; Populus - enzymology; Protein Transport; Proteins; Saccharomyces cerevisiae - metabolism; Spectrophotometry, Ultraviolet; Spectroscopy; Spectroscopy, Mossbauer; Spectrum Analysis, Raman; Subcellular Fractions - enzymology; Sulfhydryl Compounds - metabolism; Time Factors; Yeasts; chloroplast; glutaredoxin; plant; iron–sulphur protein
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2008.50

Glutaredoxins (Grxs) are small oxidoreductases that reduce disulphide bonds or protein‐glutathione mixed disulphides. More than 30 distinct grx genes are expressed in higher plants, but little is currently known concerning their functional diversity. This study presents biochemical and spectroscopic evidence for incorporation of a [2Fe–2S] cluster in two heterologously expressed chloroplastic Grxs, GrxS14 and GrxS16, and in vitro cysteine desulphurase‐mediated assembly of an identical [2Fe–2S] cluster in apo‐GrxS14. These Grxs possess the same monothiol CGFS active site as yeast Grx5 and both were able to complement a yeast grx5 mutant defective in Fe–S cluster assembly. In vitro kinetic studies monitored by CD spectroscopy indicate that [2Fe–2S] clusters on GrxS14 are rapidly and quantitatively transferred to apo chloroplast ferredoxin. These data demonstrate that chloroplast CGFS Grxs have the potential to function as scaffold proteins for the assembly of [2Fe–2S] clusters that can be transferred intact to physiologically relevant acceptor proteins. Alternatively, they may function in the storage and/or delivery of preformed Fe–S clusters or in the regulation of the chloroplastic Fe–S cluster assembly machinery.