Chen Chun-Yen, Ho Sih-Syun, Kuo Tzu-Yen, Hsieh Hsu-Liang, Cheng Yi-Sheng
Institute of Plant Biology, National Taiwan University, Taipei 10617, Taiwan.
Institute of Plant Biology, National Taiwan University, Taipei 10617, Taiwan;
Proc Natl Acad Sci U S A. 2017 Mar 7;114(10):E1815-E1824. doi: 10.1073/pnas.1609980114. Epub 2017 Feb 21.
Far-red (FR) light-coupled jasmonate (JA) signaling is necessary for plant defense and development. FR insensitive 219 (FIN219) is a member of the Gretchen Hagen 3 (GH3) family of proteins in and belongs to the adenylate-forming family of enzymes. It directly controls biosynthesis of jasmonoyl-isoleucine in JA-mediated defense responses and interacts with FIN219-interacting protein 1 (FIP1) under FR light conditions. FIN219 and FIP1 are involved in FR light signaling and are regulators of the interplay between light and JA signaling. However, how their interactions affect plant physiological functions remains unclear. Here, we demonstrate the crystal structures of FIN219-FIP1 while binding with substrates at atomic resolution. Our results show an unexpected FIN219 conformation and demonstrate various differences between this protein and other members of the GH3 family. We show that the rotated C-terminal domain of FIN219 alters ATP binding and the core structure of the active site. We further demonstrate that this unique FIN219-FIP1 structure is crucial for increasing FIN219 activity and determines the priority of substrate binding. We suggest that the increased FIN219 activity resulting from the complex form, a conformation for domain switching, allows FIN219 to switch to its high-affinity mode and thereby enhances JA signaling under continuous FR light conditions.
远红光（FR）耦合茉莉酸（JA）信号传导对于植物防御和发育至关重要。FR不敏感219（FIN219）是植物中格蕾琴·哈根3（GH3）蛋白家族的成员，属于腺苷酸形成酶家族。它在JA介导的防御反应中直接控制茉莉酰异亮氨酸的生物合成，并在FR光条件下与FIN219相互作用蛋白1（FIP1）相互作用。FIN219和FIP1参与FR光信号传导，是光与JA信号相互作用的调节因子。然而，它们的相互作用如何影响植物生理功能仍不清楚。在这里，我们展示了FIN219 - FIP1与底物结合时的原子分辨率晶体结构。我们的结果显示了意想不到的FIN219构象，并证明了该蛋白与GH3家族其他成员之间的各种差异。我们表明，FIN219旋转的C末端结构域改变了ATP结合和活性位点的核心结构。我们进一步证明，这种独特的FIN219 - FIP1结构对于提高FIN219活性至关重要，并决定了底物结合的优先级。我们认为由复合物形式产生的FIN219活性增加，即一种结构域切换的构象，使FIN219能够切换到其高亲和力模式，从而在连续FR光条件下增强JA信号传导。
