Wang Jianping, Du Bo-Ya, Zhang Xue, Qu Xiaomin, Yang Yang, Yang Zhao, Wang Yong-Fei, Zhang Peng
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China.
Key Laboratory of Plant Carbon Capture, Chinese Academy of Sciences, Shanghai, China.
Nat Plants. 2025 Mar;11(3):632-642. doi: 10.1038/s41477-025-01923-z. Epub 2025 Feb 20.
Plant cyclic nucleotide-gated channels (CNGCs) belong to the cyclic nucleotide-binding domain (CNBD) channel family, but are phylogenetically classified in a distinct branch. In contrast to their animal counterparts of K-selective or non-selective cation channels, plant CNGCs mainly mediate Ca influx and are involved in various physiological processes, such as stomatal movements, pollen-tube growth and immune responses. Here, we present the cryo-EM structure and electrophysiological analysis of plant CNGC representatives, Arabidopsis CNGC1 and CNGC5. We found that CNGC1 and CNGC5 contain a unique extracellular domain featuring disulfide bonds that is essential for channel gating via coupling of the voltage-sensing domain with the pore domain. The pore domain selectivity filter possesses a Gln residue at the constriction site that determines the Ca selectivity. Replacement of this Gln with Glu, typically observed in CNBD-type non-selective cation channels, could convert CNGC1 and CNGC5 from Ca-selective channels to non-selective cation channels permeable to Ca, Na or K. In addition, we found that the CNGC1 and CNGC5 CNBD homology domain contains intrinsic-ligand-like interactions, which may devoid the binding of cyclic nucleotides and lead to gating independent of cAMP or cGMP. This research not only provides a mechanistic understanding of plant CNGCs' function, but also adds to the comprehensive knowledge of the CNBD channels.
植物环核苷酸门控通道（CNGCs）属于环核苷酸结合结构域（CNBD）通道家族，但在系统发育上被归类于一个独特的分支。与动物中K选择性或非选择性阳离子通道的对应物不同，植物CNGCs主要介导Ca内流，并参与各种生理过程，如气孔运动、花粉管生长和免疫反应。在此，我们展示了植物CNGC代表成员拟南芥CNGC1和CNGC5的冷冻电镜结构和电生理分析。我们发现，CNGC1和CNGC5包含一个具有二硫键的独特胞外结构域，该结构域对于通过电压感应结构域与孔道结构域的偶联实现通道门控至关重要。孔道结构域选择性过滤器在收缩位点处有一个Gln残基，它决定了Ca的选择性。将这个Gln替换为Glu（这在CNBD型非选择性阳离子通道中通常可见），可以将CNGC1和CNGC5从Ca选择性通道转变为对Ca、Na或K通透的非选择性阳离子通道。此外，我们发现CNGC1和CNGC5的CNBD同源结构域包含类似内源性配体的相互作用，这可能会消除环核苷酸的结合，并导致门控独立于cAMP或cGMP。这项研究不仅提供了对植物CNGCs功能的机制性理解，也增加了对CNBD通道的全面认识。
