Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States.
Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas 75275, United States.
Biochemistry. 2021 Jan 19;60(2):95-103. doi: 10.1021/acs.biochem.0c00819. Epub 2020 Dec 18.
Plants measure light quality, intensity, and duration to coordinate growth and development with daily and seasonal changes in environmental conditions; however, the molecular details linking photochemistry to signal transduction remain incomplete. Two closely related light, oxygen, or voltage (LOV) domain-containing photoreceptor proteins, ZEITLUPE (ZTL) and FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1), divergently regulate the protein stability of circadian clock and photoperiodic flowering components to mediate daily and seasonal development. Using structural approaches, we identified that mutations at the Gly46 position led to global rearrangements of the ZTL dimer interface in the isolated ZTL-LOV domain. Specifically, G46S and G46A variants induce a 180° rotation about the ZTL-LOV dimer interface that is coupled to ordering of N- and C-terminal signaling elements. These conformational changes hinge upon rotation of a C-terminal Gln residue (Gln154) analogous to that present in light-state structures of ZTL. In contrast to other LOV proteins, a Q154L variant retains light-state interactions with GIGANTEA (GI), thereby indicating N5 protonation is not required for ZTL signaling. The results presented herein confirm a divergent signaling mechanism within ZTL, whereby steric and electronic effects following adduct formation can be sufficient for signal propagation in LOV proteins containing a Gly residue at position 46. Examination of bacterial LOV structures with Gly residues at the equivalent position suggests that mechanisms of signal transduction in LOV proteins may be fluid across the LOV protein family.
植物通过测量光质、光强和光周期来协调生长和发育，以适应环境条件的日变化和季节变化；然而，将光化学反应与信号转导联系起来的分子细节仍然不完整。两种密切相关的光、氧或电压（LOV）结构域包含的光受体蛋白，ZEITLUPE（ZTL）和FLAVIN-BINDING，KELCH REPEAT，F-BOX 1（FKF1），对生物钟和光周期开花成分的蛋白质稳定性进行了不同的调节，以介导日常和季节性发育。通过结构方法，我们确定在孤立的 ZTL-LOV 结构域中，Gly46 位置的突变导致 ZTL 二聚体界面的整体重排。具体来说，G46S 和 G46A 变体导致 ZTL-LOV 二聚体界面发生 180°旋转，这与 N 和 C 末端信号元件的有序性相关。这些构象变化取决于 C 末端 Gln 残基（Gln154）的旋转，类似于 ZTL 光态结构中的旋转。与其他 LOV 蛋白不同，Q154L 变体保留与 GIGANTEA（GI）的光态相互作用，从而表明 N5 质子化不是 ZTL 信号所必需的。本文的结果证实了 ZTL 中存在一种不同的信号转导机制，其中加合物形成后，空间和电子效应足以用于 LOV 蛋白中含有 Gly 残基的位置 46 的信号转导。对具有等效 Gly 残基的细菌 LOV 结构的检查表明，LOV 蛋白中的信号转导机制可能在整个 LOV 蛋白家族中具有流动性。
