Carazo J M, Wagenknecht T, Radermacher M, Mandiyan V, Boublik M, Frank J
Wadsworth Center for Laboratories, Albany, NY.
J Mol Biol. 1988 May 20;201(2):393-404. doi: 10.1016/0022-2836(88)90146-5.
A structural study of Escherichia coli 50 S ribosomal subunits depleted selectively of proteins L7/L12 and visualized by low-dose electron microscopy has been carried out by multivariate statistical analysis, classification schemes and the new reconstruction technique from single-exposure, random-conical tilt series. This approach has allowed us to solve the three-dimensional structure of the depleted 50 S subunits at a resolution of 3 nm-1. In addition, two distinct morphological populations of subunits (cores) have been identified in the electron micrographs analyzed and have been separately studied in three dimensions. Depleted subunits in the two morphological states present as main features common to these two structures but different from those of the non-depleted subunit (1) the absence of the stalk, (2) a rearrangement of the stalk-base that changes the overall structure of this region. This morphological change is quite noticeable and important, since this region is mapped as a part of the GTPase center. The two conformations differ mainly in the orientation of the area between the L1 region and the head (the probable localization of the peptidyl transferase center) and in the accessibility of the region located below the head. A possible relationship of these structural changes to the functional dynamics of the ribosome is suggested.
通过多变量统计分析、分类方案以及基于单次曝光、随机锥形倾斜系列的新重建技术，对选择性去除蛋白质L7/L12并通过低剂量电子显微镜观察的大肠杆菌50 S核糖体亚基进行了结构研究。这种方法使我们能够以3纳米的分辨率解析去除蛋白质后的50 S亚基的三维结构。此外，在分析的电子显微镜图像中识别出了两种不同形态的亚基群体（核心），并分别对其进行了三维研究。处于两种形态状态的去除蛋白质后的亚基呈现出这两种结构共有的主要特征，但与未去除蛋白质的亚基不同：（1）没有柄；（2）柄基部重排，改变了该区域的整体结构。这种形态变化非常明显且重要，因为该区域被定位为GTP酶中心的一部分。这两种构象的主要差异在于L1区域和头部之间区域的方向（肽基转移酶中心的可能定位）以及头部下方区域的可及性。文中提出了这些结构变化与核糖体功能动态之间的可能关系。
