Structural analysis of Arabidopsis CnfU protein: an iron-sulfur cluster biosynthetic scaffold in chloroplasts.
CnfU, a key iron-sulfur (Fe-S) cluster biosynthetic scaffold that is required for biogenesis of ferredoxin and photosystem I in chloroplasts, consists of two tandemly repeated domains in which only the N-terminal domain contains a conserved CXXC motif. We have determined the crystal structure of the metal-free dimer of AtCnfU-V from ... Arabidopsis thaliana at 1.35 A resolution. The N-terminal domains of the two monomers are linked together through two intermolecular disulfide bonds between the CXXC motifs. At the dimer interface, a total of four cysteine sulfur atoms provide a Fe-S cluster assembly site surrounded by uncharged but hydrophilic structurally mobile segments. The C-terminal domain of one monomer interacts with the N-terminal domain of the opposing monomer and thereby stabilizes dimer formation. Furthermore, Fe K-edge X-ray absorption spectroscopic analysis of the holo-CnfU dimer in solution suggests the presence of a typical [2Fe-2S]-type cluster coordinated by four thiolate ligands. Based on these data, a plausible model of the holo-AtCnfU-V dimer containing a surface-exposed [2Fe-2S] cluster assembled in the dimer interface was deduced. We propose that such a structural framework is important for CnfU to function as a Fe-S cluster biosynthetic scaffold.
Mesh Terms:
Amino Acid Sequence, Animals, Arabidopsis, Arabidopsis Proteins, Binding Sites, Chloroplasts, Conserved Sequence, Crystallography, X-Ray, Dimerization, Disulfides, Iron-Sulfur Proteins, Models, Molecular, Molecular Sequence Data, Protein Binding, Protein Structure, Quaternary, Protein Structure, Tertiary, Sequence Alignment, Spectrum Analysis, Structural Homology, Protein
Amino Acid Sequence, Animals, Arabidopsis, Arabidopsis Proteins, Binding Sites, Chloroplasts, Conserved Sequence, Crystallography, X-Ray, Dimerization, Disulfides, Iron-Sulfur Proteins, Models, Molecular, Molecular Sequence Data, Protein Binding, Protein Structure, Quaternary, Protein Structure, Tertiary, Sequence Alignment, Spectrum Analysis, Structural Homology, Protein
J. Mol. Biol.
Date: Aug. 01, 2008
PubMed ID: 18585737
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