Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Mol Cell. 2010 Aug 27;39(4):560-9. doi: 10.1016/j.molcel.2010.08.003.
Structural studies have provided detailed insights into different functional states of the ribosome and its interaction with factors involved in nascent peptide folding, processing, and targeting. However, how the translational machinery is organized spatially in native cellular environments is not yet well understood. Here we have mapped individual ribosomes in electron tomograms of intact human cells by template matching and determined the average structure of the ribosome in situ. Characteristic features of active ribosomes in the cellular environment were assigned to the tRNA channel, elongation factors, and additional densities near the peptide tunnel. Importantly, the relative spatial configuration of neighboring ribosomes in the cell is clearly nonrandom. The preferred configurations are specific for active polysomes and were largely abrogated in puromycin-treated control cells. The distinct neighbor orientations found in situ resemble configurations of bacterial polysomes in vitro, indicating a conserved supramolecular organization with implications for nascent polypeptide folding.
结构研究为核糖体的不同功能状态及其与新生肽折叠、加工和靶向相关因子的相互作用提供了详细的见解。然而，在天然细胞环境中，翻译机制如何在空间上进行组织尚不清楚。在这里，我们通过模板匹配在完整的人类细胞的电子断层扫描中绘制了单个核糖体，并确定了原位核糖体的平均结构。细胞环境中活性核糖体的特征特征被分配给 tRNA 通道、延伸因子和肽隧道附近的其他密度。重要的是，细胞中相邻核糖体的相对空间构型显然不是随机的。首选构型是活性多核糖体特有的，在嘌呤霉素处理的对照细胞中基本消失。原位发现的独特邻位取向类似于体外细菌多核糖体的构型，表明存在保守的超分子组织，对新生多肽折叠具有重要意义。
