Structural Analysis of Arabidopsis

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• 作者：Toshiki Yabe ; Eiki Yamashita ; Akihiro Kikuchi ; Kozo Morimoto ; Atsushi Nakagawa ; Tomitake Tsukihara ; Masato Nakai
• 关键词：Fe– ; S cluster ; biosynthesis ; chloroplast ; crystal structure ; EXAFS
• 刊名：Journal of Molecular Biology
• 出版年：2008
• 出版时间：1 August 2008
• 年：2008
• 卷：381
• 期：1
• 页码：160-173
• 全文大小：2928 K

文摘

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 Å 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.