专题：Nature报道
钠-钾ATP酶是一种由ATP提供动力的离子泵，能为钠离子和钾离子在动物细胞的胞质膜上形成浓度梯度。钠离子被从细胞中输出，同时钾离子被输入细胞中，产生用于很多重要生物过程、如神经细胞的动作电位的浓度梯度。
现在，来自鲨鱼直肠腺（与人的直肠腺有高度的同源性）的这种蛋白的晶体结构已被以2.4埃的分辨率确定。该结构可帮助澄清关于这种蛋白作用机制的很多细节，并且还将有助于对心脏病的认识和治疗，因为强心苷是钠-钾泵的抑制剂。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 459, 446-450 (21 May 2009) | doi:10.1038/nature07939; Received 30 July 2008; Accepted 26 February 2009
Crystal structure of the sodium–potassium pump at 2.4 Å resolution
Takehiro Shinoda1, Haruo Ogawa1, Flemming Cornelius2 & Chikashi Toyoshima1
1 Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
2 Department of Physiology and Biophysics, University of Aarhus, DK-8000 Aarhus C, Denmark
Sodium–potassium ATPase is an ATP-powered ion pump that establishes concentration gradients for Na+ and K+ ions across the plasma membrane in all animal cells by pumping Na+ from the cytoplasm and K+ from the extracellular medium1, 2. Such gradients are used in many essential processes, notably for generating action potentials. Na+, K+-ATPase is a member of the P-type ATPases, which include sarcoplasmic reticulum Ca2+-ATPase and gastric H+, K+-ATPase, among others, and is the target of cardiac glycosides. Here we describe a crystal structure of this important ion pump, from shark rectal glands, consisting of - and -subunits and a regulatory FXYD protein3, 4, all of which are highly homologous to human ones. The ATPase was fixed in a state analogous to E22K+Pi, in which the ATPase has a high affinity for K+ and still binds Pi, as in the first crystal structure of pig kidney enzyme at 3.5 Å resolution5. Clearly visualized now at 2.4 Å resolution are coordination of K+ and associated water molecules in the transmembrane binding sites and a phosphate analogue (MgF4 2-) in the phosphorylation site. The crystal structure shows that the -subunit has a critical role in K+ binding (although its involvement has previously been suggested6, 7, 8) and explains, at least partially, why the homologous Ca2+-ATPase counter-transports H+ rather than K+, despite the coordinating residues being almost identical.
