Structure of (Na+,K+)-ATPase as revealed by electron microscopy and image processing.
Structure of (Na+,K+)-ATPase as revealed by electron microscopy and image processing.
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通过电子显微镜和图像处理揭示的 (Na ,K )-ATP 酶的结构。
DOI：
10.1083/jcb.98.5.1836
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Smith,PR
中科院分区：
文献类型：
--
作者：
Mohraz,M;Smith,PR
通过电子显微镜和图像处理研究了由多种无机盐诱导的负染色、冻干和阴影结晶片（Na‘， K’）- atp酶。大量的实验已经确定了最佳晶体形成的新条件。在单晶胞中观察到两种晶体形式，一种是单体晶体，另一种是二聚体晶体。两者都显示出相同的酶单体结构。该酶也可以在其α亚基被胰蛋白酶部分蛋白水解后结晶。蛋白水解酶在与整个酶相同的条件下结晶。在完整的和蛋白水解酶的图像质量分布的比较，允许初步鉴定的位置，在单体内的α亚基。讨论了结晶酶的结构与酶的天然形式之间的关系，以及它与钙-三磷酸腺苷酶明显的密切结构关系。（Na‘， K’）-ATP酶是一种跨膜蛋白，它利用ATP水解产生的能量将K+输送到细胞内，并将Na'输送到细胞外。该分子由一个催化亚基（α， M,= 100,000）和一个糖蛋白亚基（β， M,= 50-60,000）组成。β亚基的未糖基化部分占其总分子质量的37-40,000道尔顿，其余部分由位于细胞外质表面的碳水化合物组成(4)。在哺乳动物肾脏的酶中，碳水化合物的质量占总分子量的13%。有人认为，不同来源的β亚基分子量的差异可能是由于碳水化合物组成的差异(4)。
ABSTRACT(Na', K')-ATPase was studied by electron microscopy and image processing of negatively stained and freeze-dried and shadowed crystalline sheets induced by a number of inorganic salts. Extensive experiments have identified new conditions for optimum crystal formation. Two crystal forms have been observed, one with a monomer and the other with a dimer, in the unit cell. Both show the same structure for the enzyme monomer. The enzyme can also be crystallized after partial proteolysis of its alpha subunit by trypsin. The proteolysed enzyme crystallizes under the same conditions as the whole enzyme. Comparison of the mass distributions in the images of the intact and proteolysed enzyme has allowed the tentative identification of the location of the alpha subunit within the monomer. The relationship between the structure of the crystallized enzyme and that of the enzyme in its native form is discussed, as is its apparent close structural relationship to the calcium-ATPase.(Na', K')-ATPase is a transmembrane protein that utilizes energy from ATP hydrolysis to transport K+ into and Na'outofthecellagainstconcentrationgradientsforboththeseions. The molecule consists of a catalytic subunit (alpha, M,= 100,000) and a glycoprotein subunit (beta, M,= 50-60,000). The unglycosylated part of the beta subunit makes up 37-40,000 daltons of its total molecular mass and the balance consists of carbohydrate which is located on the exoplasmic surface of the cell (4). In the enzyme from mammalian kidneys, the mass of the carbohydrate is-13% of the total molecular weight. It has been suggested that the differences in the molecular weight of the beta subunit from different sources may be due to variations in the carbohydrate composition (4).