Langmuir-Blodgett and X-ray diffraction studies of isolated photosystem II reaction centers in monolayers and multilayers: physical dimensions of the complex.
Langmuir-Blodgett and X-ray diffraction studies of isolated photosystem II reaction centers in monolayers and multilayers: physical dimensions of the complex.
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单层和多层中孤立的光系统 II 反应中心的 Langmuir-Blodgett 和 X 射线衍射研究：复合物的物理尺寸。
DOI：
10.1111/j.1751-1097.1997.tb01910.x
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发表时间：
1997
影响因子：
3.3
通讯作者：
Seibert,M
中科院分区：
文献类型：
--
作者：
Uphaus,RA;Fang,JY;Picorel,R;Chumanov,G;Wang,JY;Cotton,TM;Seibert,M
光系统II （PSII）反应中心（RC）是一种疏水的内在蛋白复合物，驱动光合作用的水氧化过程。与细菌RC复合物不同，PSII RC的X射线晶体结构是不可用的。为了确定分离的PSII RC配合物的物理尺寸，我们应用Langmuir技术确定了浓缩单层膜中分离RC的横截面积。通过检测PSII RC/Cd硬脂酸酯单层的Langmuir - Blodgett多层膜获得的低角度X射线衍射结果用于确定配合物的长度（或高度；z方向，垂直于原始膜的平面）。得到的PSII RC单体的值分别为26 nm和4.8 nm，并通过几种方法证实了多层膜中RC的结构完整性。假设是圆柱形RC结构，上述尺寸导致的预测体积约为125 nm3。根据PSII RC蛋白的已知分子量和部分比体积计算，该值非常接近118 nm3的预期体积。根据已发表的数据，我们还与theRhodobacter sphaeroidesRC进行了相同类型的比较，我们得出结论，PSII RC比细菌RC长度短得多，并且具有更规则的固体几何结构。此外，上述尺寸的PSII RC和PSII核心（RC加近端天线）蛋白的PSII膜平面外突出到管腔空间的扫描隧道显微镜成像（Seibert,Aust.）。J. PL物理学报，22,161 - 166,1995)很容易符合已知的PSII核心复合体的尺寸，其他人将其可视化为电子密度投影图。由此我们得出结论，他们的situPSII核心复合物是一个二聚体结构，包含两个拷贝的PSII RC。
The photosystem II (PSII) reaction center (RC) is a hydrophobic intrinsic protein complex that drives the water‐oxidation process of photosynthesis. Unlike the bacterial RC complex, an X‐ray crystal structure of the PSII RC is not available. In order to determine the physical dimensions of the isolated PSII RC complex, we applied Langmuir techniques to determine the cross‐sectional area of an isolated RC in a condensed monolayer film. Low‐angle X‐ray diffraction results obtained by examining Langmuir‐Blodgett multilayer films of alternating PSII RC/Cd stearate monolayers were used to determine the length (or height; z‐direction, perpendicular to the plane of the original membrane) of the complex. The values obtained for a PSII RC monomer were 26 nm2and 4.8 nm, respectively, and the structural integrity of the RC in the multilayer film was confirmed by several approaches. Assuming a cylindrical‐type RC structure, the above dimensions lead to a predicted volume of about 125 nm3. This value is very close to the expected volume of 118 nm3, calculated from the known molecular weight and partial specific volume of the PSII RC proteins. This same type of comparison was also made with theRhodobacter sphaeroidesRC based on published data, and we conclude that the PSII RC is much shorter in length and has a more regular solid geometric structure than the bacterial RC. Furthermore, the above dimensions of the PSII RC and those of PSII core (RC plus proximal antenna) proteins protruding outside the plane of the PSII membrane into the lumenal space as imaged by scanning tunneling microscopy (Seibert,Aust. J. PL Physiol.22,161–166, 1995) fit easily into the known dimensions of the PSII core complex visualized by others as electron‐density projection maps. From this we conclude that thein situPSII core complex is a dimeric structure containing two copies of the PSII RC.