Higher Order Structure Contributes to Specific Differences in Redox Potential and Electron Transfer Efficiency of Root and Leaf Ferredoxins

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• 作者：Ping Gou ; Guy T. Hanke ; Yoko Kimata-Ariga ; Daron M. Standley ; Atsushi Kubo ; Isao Taniguchi ; Haruki Nakamura ; Toshiharu Hase
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：December 5, 2006
• 年：2006
• 卷：45
• 期：48
• 页码：14389 - 14396
• 全文大小：352K
• 年卷期：v.45,no.48(December 5, 2006)
• ISSN：1520-4995

文摘

Plant type ferredoxin (Fd) is a small [2Fe-2S] cluster containing electron-transfer protein witha highly negative redox potential. Higher plants contain different iso-protein types of Fd in roots andleaves, reflecting the difference in redox cascades between these two tissues. We have combined subdomainsof leaf and root Fds in recombinant chimeras, to examine structural effects and the relationship betweengroups of residues on redox potential, electron transfer, and protein-protein interactions. All chimerashad redox potentials that were intermediate to the wild type leaf and root Fds. Surprisingly, the largestdifferences resulted from exchange of the N-terminus, the region farthest from the redox center. Homologymodeling and energy minimization calculations suggest that the N-terminal chimeras may indirectlyinfluence redox potentials by structurally perturbing the active site. Measurements of electron transportand protein interaction indicate that synergistic interaction between the C- and N-terminal of root Fdbestows a specific high affinity for accepting electrons in the root type electron cascade, and that there isdiscrimination against photosynthetic electron donation to root Fd based on the C-terminus of the molecule.Taken together, the experimental and computational studies support a model in which higher order structurecontributes to iso-protein specific interaction and electron-transfer properties.