An X-ray diffraction analysis of oriented lipid multilayers containing basic proteins.
An X-ray diffraction analysis of oriented lipid multilayers containing basic proteins.
复制标题
含有碱性蛋白质的定向脂质多层的 X 射线衍射分析。
DOI：
10.1016/0005-2736(85)90556-5
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
N. Franks
中科院分区：
文献类型：
--
作者：
W. Macnaughtan;K. Snook;E. Caspi;N. Franks
用X射线衍射法研究了含有碱性蛋白质的脂双层的结构。利用Langmuir-Blodgett方法，固体载体通过在空气/水界面保持恒定表面压力的脂单分子层，形成了高度有序的多层样品。如果脂单分子层含有酸性脂类，则水相亚相中的碱性蛋白与单分子膜一起转移并并入多膜堆叠。在含有和不含有多聚赖氨酸、细胞色素和中枢神经系统髓鞘碱性蛋白的情况下，脑苷硫酸盐和40%(摩尔)胆固醇的多层膜都记录了X射线衍射图。膜上的电子密度分布的分辨率在6？到12？之间。通过胆固醇与溴化胆固醇类似物的同象交换，所有的膜轮廓都被置于电子密度的绝对标度上。脑苷脂硫酸盐/胆固醇双层结合的各种碱性蛋白的分布和构象有很大的不同。聚赖氨酸以完全延伸链的形式附着在脂质双层表面，而细胞色素则保持其固有的结构，并以近乎垂直于膜平面的短轴附着于双层表面。髓磷脂碱性蛋白以延伸分子的形式与脂头基团紧密结合，但其尺寸垂直于膜的平面。15与溶液中发现的相当程度的二级结构是一致的。在膜平面，髓鞘碱性蛋白延伸到大约2500ä2的区域。蛋白质没有显著地渗透到双层的碳氢化合物区域，或者实际上，超出了脑苷硫酸盐分子的硫酸盐基团的位置。
X-ray diffraction techniques have been used to study the structures of lipid bilayers containing basic proteins. Highly ordered multilayer specimens have been formed by using the Langmuir-Blodgett method in which a solid support is passed through a lipid monolayer held at constant surface pressure at an air/water interface. If the lipid monolayer contains acidic lipids then basic proteins in the aqeous subphase are transferred with the monolayer and incorporated into the multi-membrane stack. X-ray diffraction patterns have been recorded from multilayers of cerebroside sulphate and 40% (molar) cholesterol both with and without polylysine, cytochromecand the basic protein from central nervous system myelin. Electron density profiles across the membranes have been derived at between 6 Å and 12 Å resolution. All of the membrane profiles have been placed on an absolute scale of electron density by the isomorphous exchange of cholesterol with a brominated cholesterol analog. The distributions and conformations of the various basic proteins incorporated within the cerebroside sulphate/cholesterol bilayer are very different. Polylysine attaches to the surface of the lipid bilayer as a fully extended chain while cytochromecmaintains its native structure and attaches to the bilayer surface with its short axis approximately perpendicular to the membrane plane. The myelin basic protein associates intimately with the lipid headgroups in the form of an extended molecule, yet its dimension perpendicular to the plane of the membrane of approx. 15 Å is consistent with the considerable degree of secondary structure found in solution. In the membrane plane, the myelin basic protein extends to cover an area of about 2500 Å2. There is no significant penetration of the protein into the hydrocarbon region of the bilayer or, indeed, beyond the position of the sulphate group of the cerebroside sulphate molecule.