期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 381, 期 1, 页码 160-173出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2008.05.072
关键词
Fe-S cluster; biosynthesis; chloroplast; crystal structure; EXAFS
CnfU, a key iron-sulfur (Fe-S) cluster biosynthetic scaffold that is required for biogenesis of ferredoxin and photosystem I in choloroplasts, 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 angstrom 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. (C) 2008 Elsevier Ltd. All rights reserved.
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