Liu Kun, Li Legong, Luan Sheng
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Plant J. 2006 Apr;46(2):260-8. doi: 10.1111/j.1365-313X.2006.02689.x.
Most K+ channels in plants are structurally classified into the Shaker family named after the shaker K+ channel in Drosophila. Plant K+ channels function in many physiological processes including osmotic regulation and K+ nutrition. An outwardly rectifying K+ channel, SKOR, mediates the delivery of K+ from stelar cells to the xylem in the roots, a critical step in the long-distance distribution of K+ from roots to the upper parts of the plant. Here we report that SKOR channel activity is strictly dependent on intracellular K+ concentrations. Activation by K+ did not affect the kinetics of voltage dependence in SKOR, indicating that a voltage-independent gating mechanism underlies the K+ sensing process. Further analysis showed that the C-terminal non-transmembrane region of the SKOR protein was required for this sensing process. The intracellular K+ sensing mechanism couples SKOR activity to K+ nutrition status in the 'source cells', thereby establishing a supply-based unloading system for the regulation of K+ distribution.
植物中的大多数钾离子通道在结构上被归类为以果蝇中的震颤钾离子通道命名的Shaker家族。植物钾离子通道在许多生理过程中发挥作用，包括渗透调节和钾营养。一种外向整流钾离子通道SKOR介导钾离子从根部的中柱细胞向木质部的运输，这是钾离子从根部向植物上部进行长距离运输的关键步骤。在此，我们报道SKOR通道活性严格依赖于细胞内钾离子浓度。钾离子激活并不影响SKOR中电压依赖性的动力学，这表明钾离子传感过程存在一种不依赖电压的门控机制。进一步分析表明，SKOR蛋白的C端非跨膜区域是该传感过程所必需的。细胞内钾离子传感机制将SKOR活性与“源细胞”中的钾营养状况相耦合，从而建立了一个基于供应的卸载系统来调节钾离子分布。
