Structural organization of (Na+ + K+)-ATPase in purified membranes.
Structural organization of (Na+ + K+)-ATPase in purified membranes.
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DOI：
10.1083/jcb.98.5.1851
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发表时间：
1984-05
影响因子：
7.8
通讯作者：
Freytag, W
中科院分区：
文献类型：
--
作者：
Zampighi, G;Kyte, J;Freytag, W
用阴性染色和薄切片法研究了晶体膜结合(Na+ + K+)- atp酶的结构组织。在确定的离子条件下，酶分子被诱导在膜片段内形成晶体阵列。结晶后酶保持充分活性。晶体标本的阴性染色和计算机图像处理确定了两个离散的晶体阵列。其中一个阵列的单元格尺寸足够大，可以容纳α - β原聚体；另一组的，一个（α β）2双质子聚体。晶体部分的薄片含有由两个相对的质膜形成的独特的膜复合物。该络合物中的成对膜由15 nm的中心间距隔开，其中包含连接膜表面的均匀间隔；整个结构的总厚度为22-25 nm。来自蓖麻的凝集素，一种与(Na+ + K+)- atp酶β亚基的碳水化合物部分结合的凝集素，装饰着复合物的自由表面。因此，这种成对膜的复合体是酶的细胞质结构域之间相互作用的结果。从这些结构的尺寸测量中，我们估计酶的总长度沿垂直于膜平面的轴约为11.5 nm，分子在细胞质表面上的突出（约5 nm）比在胞质表面上的突出（约2 nm）更多。
The structural organization of crystalline, membrane-bound (Na+ + K+)- ATPase was studied by negative staining and thin sectioning. The enzyme molecules were induced to form crystalline arrays within fragments of membrane by incubation in defined ionic conditions. The enzyme remained fully active after crystallization. Negative staining and computer processing of images of the crystalline specimens identified two discrete crystalline arrays. The dimensions of the unit cell of one of the arrays were large enough to accommodate an alpha beta protomer; those of the other array, an (alpha beta)2 diprotomer . Thin sections of the crystalline fraction contained a unique membrane complex that was formed from two apposed plasma membranes. The paired membranes in this complex were separated by a center-to-center space of 15 nm containing evenly spaced septa that connected the membrane surfaces; the overall thickness of the entire structure was 22-25 nm. The agglutinin from Ricinus communis, a lectin that binds to the carbohydrate moiety of the beta-subunit of (Na+ + K+)-ATPase, decorated the free surfaces of the complex. Therefore, this complex of paired membranes is the result of interactions between the cytoplasmic domains of the enzyme. From measurements of the dimensions of these structures, we estimate the overall length of the enzyme to be approximately 11.5 nm along the axis perpendicular to the plane of the membrane, and the molecular protrudes more (approximately 5 nm) on the cytoplasmic surface than on the extracytoplasmic surface (approximately 2 nm).