Chloroplast monothiol glutaredoxins as scaffold proteins for the assembly and delivery of [2Fe-2S] clusters.
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.
Bandyopadhyay
Sibali
S
Department of Chemistry, Centre for Metalloenzyme Studies, University of Georgia, Athens, GA, USA.
Gama
Filipe
F
Molina-Navarro
Maria Micaela
MM
Gualberto
José Manuel
JM
Claxton
Ronald
R
Naik
Sunil G
SG
Huynh
Boi Hanh
BH
Herrero
Enrique
E
Jacquot
Jean Pierre
JP
Johnson
Michael K
MK
Rouhier
Nicolas
N
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins; D001665:Binding Sites; D002736:Chloroplasts / Q000201:enzymology*; D002942:Circular Dichroism; D005288:Ferredoxins / Q000378:metabolism; D005816:Genetic Complementation Test; D054477:Glutaredoxins / Q000737:chemistry / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D032107:Populus / Q000201:enzymology*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D015204:Spectroscopy, Mossbauer; D013059:Spectrum Analysis, Raman; D013347:Subcellular Fractions / Q000201:enzymology; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013997:Time Factors
D001059:Apoproteins; D029681:Arabidopsis Proteins; D005288:Ferredoxins; D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; D013438:Sulfhydryl Compounds