CRYSTALLINE-STRUCTURE OF GAS VESICLE WALL FROM ANABAENA-FLOS-AQUAE
CRYSTALLINE-STRUCTURE OF GAS VESICLE WALL FROM ANABAENA-FLOS-AQUAE
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DOI：
10.1016/0022-2836(76)90106-6
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发表时间：
1976-01-01
影响因子：
5.6
通讯作者：
WALSBY, AE
中科院分区：
文献类型：
--
作者：
BLAUROCK, AE;WALSBY, AE
从A.用X射线衍射法研究了絮凝剂的结构。电子显微镜先前表明，气泡是细长的形状，薄壁具有与长轴成直角的规则条纹（肋）。定向完整囊泡样品的X射线衍射图包括许多尖锐的反射，这归因于壁平面中的规则结构。在对囊泡长轴的不完美对齐进行校正后，可以看到平面内反射都位于平行于长轴的几条规则间隔的线上。该结果第一次表明，存在沿每个肋沿着规则间隔的亚基，每11埃1个亚基。平面内反射沿着每条线的间隔与46埃的肋周期一致。第11章.安重复，连同46. ANG。肋与肋之间的重复距离和约20埃的平均壁厚，定义子单元的体积。假设构成壁的蛋白质密度的合理值，所示亚基的MW约为8000 g/mol。X射线数据还表明，大部分蛋白质在β-片状构象在这种结构中，存在平行或反平行的多肽链，它们以规则的方式彼此氢键合以形成薄片。假设壁包含β- 2层片材，一层在另一层的顶部，每层中的链倾斜35 °。相对于囊泡的长轴，我们可以解释许多X射线观察结果：布拉格间距为4.7埃的定向弧，其是每层中相邻链的轴之间的距离;衍射以6至7埃的间距沿链的方向取向，其是二肽单元沿链沿着的重复距离;重复，其是沿着沿着每个肋的成对链的重复距离;以及与壁平面成直角并以10埃的间距为中心的宽衍射带，这对于两个板的中间平面之间的距离是合理的值。此外，我们还可以找到剩余的晶格参数，即与相邻肋中的子单元中心相关的角度。因此，连接这些中心的最短直线形成86 °角。肋骨的方向。
The gas vesicles isolated from A. flos-aquae were studied by X-ray diffraction. EM previously showed that the gas vesicles are elongated shapes, with a thin wall having regular striations (ribs) at right-angles to the long axis. The X-ray diffraction pattern from a specimen of oriented, intact vesicles includes a number of sharp reflections which are attributed to regular structure in the plane of the wall. After correcting for the imperfect alignment of the long axes of the vesicles, the in-plane reflections are all seen to lie on a few, regularly spaced lines parallel to the long axis. This result shows for the 1st time that there are subunits regularly spaced along each rib, 1 subunit every 11 .ANG.. The spacing of the in-plane reflections along each line is consistent with a rib periodicity of 46 .ANG.. The 11 .ANG. repeat, together with the 46 .ANG. repeating distance from rib to rib and the average wall thickness of about 20 .ANG., define a volume for the subunit. Assuming a reasonable value for the density of the protein making up the wall, the MW of the subunit indicated is about 8000 g/mol. The X-ray data also indicate that a large part of the protein is in the .beta.-sheet conformation. In this structure there are parallel, or anti-parallel, polypeptide chains which are hydrogen-bonded to one another in a regular way to form a thin sheet. Assuming the wall contains .beta.-sheet in 2 layers, one on top of the other and with the chains in each layer tilted at 35.degree. to the long axis of the vesicle, we can explain a number of the X-ray observations: oriented arcs with a Bragg spacing of 4.7 .ANG., which is the distance between the axes of neighboring chains in each layer; diffraction oriented in the direction of the chains at a spacing of 6 to 7 .ANG., which is the repeating distance of the dipeptide unit along the chain; the 11 .ANG. repeat, which is the repeating distance of pairs of chains along each rib; and a broad band of diffraction at right-angles to the plane of the wall and centered at a spacing of 10 .ANG., which is a reasonable value for the distance between the mid-planes of the 2 sheets. Moreover, we can also find the remaining lattice parameter, the angle relating the centers of the subunits in neighboring ribs. Thus the shortest line joining the centers makes an angle of 86.degree. with the direction of the ribs.