State Key Laboratory for Agrobiotechnology, Frontiers Science Center for Molecular Design Breeding, College of Biological Sciences, China Agricultural University, Beijing, China.
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China.
Nat Commun. 2022 Sep 27;13(1):5682. doi: 10.1038/s41467-022-33420-8.
The voltage-gated potassium channel AKT1 is responsible for primary K uptake in Arabidopsis roots. AKT1 is functionally activated through phosphorylation and negatively regulated by a potassium channel α-subunit AtKC1. However, the molecular basis for the modulation mechanism remains unclear. Here we report the structures of AKT1, phosphorylated-AKT1, a constitutively-active variant, and AKT1-AtKC1 complex. AKT1 is assembled in 2-fold symmetry at the cytoplasmic domain. Such organization appears to sterically hinder the reorientation of C-linkers during ion permeation. Phosphorylated-AKT1 adopts an alternate 4-fold symmetric conformation at cytoplasmic domain, which indicates conformational changes associated with symmetry switch during channel activation. To corroborate this finding, we perform structure-guided mutagenesis to disrupt the dimeric interface and identify a constitutively-active variant Asp379Ala mediates K permeation independently of phosphorylation. This variant predominantly adopts a 4-fold symmetric conformation. Furthermore, the AKT1-AtKC1 complex assembles in 2-fold symmetry. Together, our work reveals structural insight into the regulatory mechanism for AKT1.
电压门控钾通道 AKT1 负责拟南芥根中的初级 K 吸收。AKT1 通过磷酸化被功能性激活，并受钾通道 α 亚基 AtKC1 负调控。然而，该调节机制的分子基础仍不清楚。本研究报道了 AKT1、磷酸化 AKT1、组成型激活变体以及 AKT1-AtKC1 复合物的结构。AKT1 在细胞质域以 2 重对称形式组装。这种组织似乎在空间上阻碍了 C 接头在离子渗透过程中的重新定向。磷酸化 AKT1 在细胞质域中采用交替的 4 重对称构象，表明在通道激活过程中与对称转换相关的构象变化。为了证实这一发现，我们进行了结构导向的突变，破坏二聚体界面，并鉴定出组成型激活变体 Asp379Ala 独立于磷酸化介导 K 渗透。该变体主要采用 4 重对称构象。此外，AKT1-AtKC1 复合物以 2 重对称形式组装。综上，本工作揭示了 AKT1 调节机制的结构见解。
