Dekker J P, Betts S D, Yocum C F, Boekema E J
Department of Biology, University of Michigan, Ann Arbor 48109-1048.
Biochemistry. 1990 Apr 3;29(13):3220-5. doi: 10.1021/bi00465a011.
A photosystem II complex containing the reaction center proteins D1 and D2, a 47-kDa chlorophyll-binding protein (CP47), and cytochrome b-559 was isolated with high yield, purity, and homogeneity; small but well-ordered two-dimensional crystals were prepared from the particles. The crystals and the isolated particles were analyzed by electron microscopy using negatively stained specimens. The information of 20 different digitized crystals was combined by alignment programs based on correlation methods to obtain a final average. The calculated diffraction pattern, with spots up to a resolution of 2.5 nm, and the optical diffraction pattern of a single crystal indicate that the plane group is p22121 (also called p2gg) and that the unit cell is rectangular with parameters of 23.5 x 16.0 nm, containing four stain-excluding monomers (two face-up and two face-down). In projection, the monomers have an asymmetrical shape with a length of 10 nm, a maximal width of 7.5 nm, and a height of 6 nm; their molecular mass is 175 +/- 40 kDa.
我们以高产率、高纯度和高均一性分离出了一种光系统II复合物，它包含反应中心蛋白D1和D2、一种47 kDa的叶绿素结合蛋白（CP47）以及细胞色素b - 559；并从这些颗粒制备出了小而有序的二维晶体。利用负染标本通过电子显微镜对晶体和分离出的颗粒进行了分析。基于相关方法的比对程序将20个不同数字化晶体的信息进行合并以获得最终平均值。计算得到的衍射图谱，其斑点分辨率高达2.5 nm，以及单个晶体的光学衍射图谱表明，平面群为p22121（也称为p2gg），晶胞为矩形，参数为23.5×16.0 nm，包含四个不被染色的单体（两个面朝上和两个面朝下）。在投影中，单体呈不对称形状，长度为10 nm，最大宽度为7.5 nm，高度为6 nm；它们的分子量为175 +/- 40 kDa。
