Ternary Protein Complex of Ferredoxin, Ferredoxin:Thioredoxin Reductase, and Thioredoxin Studied by Paramagnetic NMR Spectroscopy

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• 作者：Xingfu Xu ; Peter Schrmann ; Jung-Sung Chung ; Mathias A. S. Hass ; Sung-Kun Kim ; Masakazu Hirasawa ; Jatindra N. Tripathy ; David B. Knaff ; Marcellus Ubbink
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：December 9, 2009
• 年：2009
• 卷：131
• 期：48
• 页码：17576-17582
• 全文大小：356K
• 年卷期：v.131,no.48(December 9, 2009)
• ISSN：1520-5126

文摘

In oxygenic photosynthetic cells, carbon metabolism is regulated by a light-dependent redox signaling pathway through which the light signal is transmitted in the form of electrons via a redox chain comprising ferredoxin (Fd), ferredoxin:thioredoxin reductase (FTR), and thioredoxin (Trx). Trx affects the activity of a variety of enzymes via dithiol oxidation and reduction reactions. FTR reduces an intramolecular disulfide bridge of Trx, and Trx reduction involves a transient cross-link with FTR. NMR spectroscopy was used to investigate the interaction of Fd, FTR, and an m-type Trx. NMR titration experiments indicate that FTR uses distinct sites to bind Fd and Trx simultaneously to form a noncovalent ternary complex. The orientation of Trx-m relative to FTR was determined from the intermolecular paramagnetic broadening caused by the [4Fe-4S] cluster of FTR. Two models of the noncovalent binary complex of FTR/Trx-m based on the paramagnetic distance restraints were obtained. The models suggest that either a modest or major rotational movement of Trx must take place when the noncovalent binary complex proceeds to the covalent complex. This study demonstrates the complementarity of paramagnetic NMR and X-ray diffraction of crystals in the elucidation of dynamics in a transient protein complex.