Institute for Quantitative Biosciences, The University of Tokyo, Japan.
Department of Biomedicine, Aarhus University, Denmark.
FEBS Lett. 2022 Oct;596(19):2513-2524. doi: 10.1002/1873-3468.14437. Epub 2022 Jul 6.
Na ,K -ATPase (NKA) is one of the most important members of the P-type ion-translocating ATPases and plays a pivotal role in establishing electrochemical gradients for Na and K across the cell membrane. Presented here is a 3.3 Å resolution structure of NKA in the E2·2K state solved by cryo-electron microscopy. It is a stable state with two occluded K after transferring three Na into the extracellular medium and releasing inorganic phosphate bound to the cytoplasmic P domain. We describe how the extracellular ion pathway wide open in the E2P state becomes closed and locked in E2·2K , linked to events at the phosphorylation site more than 50 Å away. We also show, although at low resolution, how ATP binding to NKA in E2·2K relaxes the gating machinery and thereby accelerates the transition into the next step, that is, the release of K into the cytoplasm, more than 100 times.
钠钾泵（NKA）是 P 型离子转运 ATP 酶家族中最重要的成员之一，在跨细胞膜建立钠和钾的电化学梯度方面发挥着关键作用。本文展示了通过冷冻电镜解析的处于 E2·2K 状态下的 NKA 的 3.3 Å 分辨率结构。这是一个稳定的状态，在将三个钠转移到细胞外介质中并释放与细胞质 P 结构域结合的无机磷酸后，有两个被封闭的钾。我们描述了 E2P 状态下细胞外离子通道的打开状态如何转变为关闭和锁定的 E2·2K 状态，这与远在 50Å 之外的磷酸化位点上的事件有关。我们还展示了，尽管分辨率较低，NKA 在 E2·2K 中与 ATP 的结合如何放松门控机制，从而加速进入下一步，即将钾释放到细胞质中，速度提高了 100 多倍。
