Structural studies of Na,K-ATPase.
Structural studies of Na,K-ATPase.
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Na,K-ATP酶的结构研究。
DOI：
10.1111/j.1749-6632.1986.tb34506.x
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发表时间：
1986
影响因子：
5.2
通讯作者：
Smith,PR
中科院分区：
文献类型：
--
作者：
Mohraz,M;Yee,M;Smith,PR
钠离子和钾离子激活的三磷酸腺苷酶 (Na, K-ATPase) 是一组转运 ATP 酶之一，它将 ATP 的水解与离子跨膜的主动转运结合起来。这些包括细胞膜和肌浆网的 Ca-ATP 酶、胃 H、K-ATP 酶以及细菌和真菌膜的 H-ATP 酶。 Na, K-ATP 酶和 H, K-ATP 酶起到双向泵的作用，因为它们在细胞膜上双向运输离子。已经证明，在红细胞中，Na、K-ATP酶利用一个 ATP 分子水解产生的能量，将 3 个 Na+ 运出细胞，将 2 个 K+ 运入细胞。's2 该酶由两条多肽链组成：01 (M, 110,000) 是催化亚基，p (M, 50-60,000) 是一种糖蛋白，其确切功能尚不清楚。这两个亚基以 1:1 摩尔化学计量存在。~~~ 从许多组织中纯化 Na, K-ATP 酶^^-^ 已允许对其特性进行广泛的研究（参见参考文献 9-12 中的评论）。 Post 和他的合作者首先提出的模型^,"^'^ 已被详细阐述，以解释许多现有的动力学和生化观察结果。根据该模型，酶在泵送循环期间可以以两种主要构象状态存在。在 El 形式中，它对 Na+ 和 ATP 具有亲和力，并由这些配体稳定。在 E2 形式中，较高的能量状态，它结合 K+ 和/或无机磷酸盐，并由这些离子稳定。E1 和 E2 具有不同的构象：在 Na+ 存在下，胰蛋白酶消化产生的碎片模式与在 K+ 存在下的蛋白水解不同。'5J6 在过去五年中出现了有关 Na, K-ATP 酶的重要新结构信息。此外，在膜碎片中诱导酶二维晶体的方案的发现为通过电子显微镜和图像分析进行结构研究开辟了道路。然而，泵的寡聚结构仍然是一个有争议的话题。虽然一些研究提供的数据表明启动子 (a $) 能够主动转运，但其他研究指出二聚体 (010)~ 具有功能性。在我们的实验室中，我们对 Na、K-ATP 酶进行了结构研究，并设计了两种方法的结合，产生了有趣的结果。结果解决了功能单元寡聚形式的问题，并为 Na+ 和 K+ 的运输如何发生提供了建议。根据这些结果，我们提出了 Na、K 功能的模型。
Sodium and potassium ion activated adenosine-triphosphatase (Na, K-ATPase) is one of a group of transport ATPases that couple the hydrolysis of ATP to the active transport of ions across membranes. These include Ca-ATPases of the cell membrane and the sarcoplasmic reticulum, the gastric H, K-ATPase, and the H-ATPase of bacterial and fungal membranes. Na, K-ATPase and H, K-ATPase function as bidirectional pumps, since they transport ions in both directions across the cell membrane. It has been demonstrated that in red blood cells Na, K-ATPase uses the energy from the hydrolysis of one ATP molecule to transport 3 Na+ out of the cell and 2 K+ into the cell.'s2 The enzyme consists of two polypeptide chains: 01 (M, 110,000) is the catalytic subunit, and p (M, 50-60,000) a glycoprotein whose exact function is not yet understood. The two subunits exist in a 1: l molar stoi~ hiometry.~~~ Purification of Na, K-ATPase from a number of tissue^^-^ has allowed extensive studies of its properties (see reviews in REFERENCES 9-12). A model, first proposed by Post and his collaborator^,"^'^ has been elaborated to explain many of the existing kinetic and biochemical observations. According to this model the enzyme can exist in two major conformational states during the pumping cycle. In the El form it has affinity for Na+ and ATP and is stabilized by these ligands. In the E2 form, the higher energy state, it binds K+ and/or inorganic phosphate and is stabilized by these ions. El and E2 have different conformations: digestion by trypsin in the presence of Na+ produces a different fragmentation pattern than proteolysis in the presence of K+.'5J6 Significant new structural information concerning the Na, K-ATPase has emerged in the past five years. The amino acid sequences of have been determined. Furthermore, the discovery of a scheme to induce two-dimensional crystals of the enzyme in membrane fragments2* has opened the way for structural studies by electron microscopy and image analysis. A number of investigators have reported structural analysis of the enzyme in pr~ jection~~-~~ as well as preliminary data on its three-dimensional str~ cture.~~'~'The oligomeric structure of the pump has, however, remained a subject of controversy. While some studies have produced data to suggest that the promoter (a $) is capable of active transport, 28s29 others have pointed to the dimer (010)~ as the functionalIn our laboratory we have conducted structural studies of Na, K-ATPase and biochemical experiments designed to complement them. The combination of the two approaches has yielded interesting results that address the question of the oligomeric form of the functional unit and offer suggestions as to how the transport of N a+ and K+ might occur. From these results we propose a model for the functioning of the Na, K