Department of Biological Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Department of Biochemistry, University of Oxford, Oxford, UK.
Nat Commun. 2022 May 6;13(1):2505. doi: 10.1038/s41467-022-30292-w.
In the light reaction of plant photosynthesis, modulation of electron transport chain reactions is important to maintain the efficiency of photosynthesis under a broad range of light intensities. VCCN1 was recently identified as a voltage-gated chloride channel residing in the thylakoid membrane, where it plays a key role in photoreaction tuning to avoid the generation of reactive oxygen species (ROS). Here, we present the cryo-EM structures of Malus domestica VCCN1 (MdVCCN1) in nanodiscs and detergent at 2.7 Å and 3.0 Å resolutions, respectively, and the structure-based electrophysiological analyses. VCCN1 structurally resembles its animal homolog, bestrophin, a Ca-gated anion channel. However, unlike bestrophin channels, VCCN1 lacks the Ca-binding motif but instead contains an N-terminal charged helix that is anchored to the lipid membrane through an additional amphipathic helix. Electrophysiological experiments demonstrate that these structural elements are essential for the channel activity, thus revealing the distinct activation mechanism of VCCN1.
在植物光合作用的光反应中，电子传递链反应的调节对于在广泛的光强范围内维持光合作用的效率非常重要。VCCN1 最近被鉴定为一种位于类囊体膜中的电压门控氯离子通道，它在光反应调节中起着关键作用，以避免活性氧（ROS）的产生。在这里，我们分别以 2.7Å 和 3.0Å 的分辨率呈现了拟南芥 VCCN1（MdVCCN1）在纳米盘和去污剂中的冷冻电镜结构，以及基于结构的电生理分析。VCCN1 的结构与它的动物同源物，壁细胞钙离子激活氯离子通道（bestrophin）相似，但是与壁细胞钙离子激活氯离子通道不同的是，VCCN1 缺乏 Ca 结合基序，但它含有一个 N 端带电荷的螺旋，通过另一个双亲螺旋锚定在脂膜上。电生理实验表明，这些结构元件对于通道活性是必不可少的，从而揭示了 VCCN1 的独特激活机制。
