title: Arabidopsis thaliana Nfu2 accommodates [2Fe-2S] or [4Fe-4S] clusters and is competent for in vitro maturation of chloroplast [2Fe-2S] and [4Fe-4S] cluster-containing proteins.
abstract: Nfu-type proteins are essential in the biogenesis of iron-sulfur (Fe-S) clusters in numerous organisms. A number of phenotypes including low levels of Fe-S cluster incorporation are associated with the deletion of the gene encoding a chloroplast-specific Nfu-type protein, Nfu2 from Arabidopsis thaliana (AtNfu2). Here, we report that recombinant AtNfu2 is able to assemble both [2Fe-2S] and [4Fe-4S] clusters. Analytical data and gel filtration studies support cluster/protein stoichiometries of one [2Fe-2S] cluster/homotetramer and one [4Fe-4S] cluster/homodimer. The combination of UV-visible absorption and circular dichroism and resonance Raman and Mössbauer spectroscopies has been employed to investigate the nature, properties, and transfer of the clusters assembled on Nfu2. The results are consistent with subunit-bridging [2Fe-2S](2+) and [4Fe-4S](2+) clusters coordinated by the cysteines in the conserved CXXC motif. The results also provided insight into the specificity of Nfu2 for the maturation of chloroplastic Fe-S proteins via intact, rapid, and quantitative cluster transfer. [2Fe-2S] cluster-bound Nfu2 is shown to be an effective [2Fe-2S](2+) cluster donor for glutaredoxin S16 but not glutaredoxin S14. Moreover, [4Fe-4S] cluster-bound Nfu2 is shown to be a very rapid and efficient [4Fe-4S](2+) cluster donor for adenosine 5'-phosphosulfate reductase (APR1), and yeast two-hybrid studies indicate that APR1 forms a complex with Nfu2 but not with Nfu1 and Nfu3, the two other chloroplastic Nfu proteins. This cluster transfer is likely to be physiologically relevant and is particularly significant for plant metabolism as APR1 catalyzes the second step in reductive sulfur assimilation, which ultimately results in the biosynthesis of cysteine, methionine, glutathione, and Fe-S clusters.
authors.affiliation: Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia, 30602, United States.
authors.forename: Huanyao
authors.initials: H
authors.lastname: Gao
authors.forename: Sowmya
authors.initials: S
authors.lastname: Subramanian
authors.forename: Jérémy
authors.initials: J
authors.lastname: Couturier
authors.forename: Sunil G
authors.initials: SG
authors.lastname: Naik
authors.forename: Sung-Kun
authors.initials: SK
authors.lastname: Kim
authors.forename: Thomas
authors.initials: T
authors.lastname: Leustek
authors.forename: David B
authors.initials: DB
authors.lastname: Knaff
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Wu
authors.forename: Florence
authors.initials: F
authors.lastname: Vignols
authors.forename: Boi Hanh
authors.initials: BH
authors.lastname: Huynh
authors.forename: Nicolas
authors.initials: N
authors.lastname: Rouhier
authors.forename: Michael K
authors.initials: MK
authors.lastname: Johnson
mesh_terms: D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D002736:Chloroplasts / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism; D054477:Glutaredoxins / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D029681:Arabidopsis Proteins; D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; C493953:Nfu2 protein, Arabidopsis; D050862:Oxidoreductases Acting on Sulfur Group Donors; C019618:adenylylsulfate reductase; D004720:Endonucleases; C582684:GRXS16 protein, Arabidopsis
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