Structure of Halothiobacillus neapolitanus carboxysomes by cryo-electron tomography
Structure of Halothiobacillus neapolitanus carboxysomes by cryo-electron tomography
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DOI：
10.1016/j.jmb.2006.09.024
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发表时间：
2006-12-01
影响因子：
5.6
通讯作者：
Shively, Jessup M.
中科院分区：
文献类型：
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作者：
Schmid, Michael F.;Paredes, Angel M.;Shively, Jessup M.
羧基体是由蛋白质外壳组成的多面体，其中填充有核酮糖1，5-二磷酸羧化酶/加氧酶（RuBisCO）。它们存在于所有蓝细菌和一些化能自养细菌的细胞质中。以往对那不勒斯嗜盐硫杆菌和敏捷硝化杆菌的研究表明，其羧基体的结构为二十面体或十二面体。为了更确切地确定蛋白质的外壳结构，纯化的H。通过冷冻电子断层扫描和扫描透射电子显微镜（STEM）重新检查那不勒斯羧酶体。由于电子显微镜中有限的倾斜角，断层重建失真。在计算提取的羧基体的3D方向搜索和平均中进行校正，以最大限度地减少缺失数据的影响。结果表明，H. Neapolitanus carboxysomes的大小和质量变化很大，分别如冷冻电子断层扫描和STEM质量测量所示。我们已经对齐和平均carboxysomes在几个大小类的3D断层重建的方法，不模型偏置。平均值揭示了壳的二十面体对称性，但不是所有尺寸级的壳内密度。(c)2006爱思唯尔有限公司保留所有权利。
Carboxysomes are polyhedral bodies consisting of a proteinaceous shell filled with ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO). They are found in the cytoplasm of all cyanobacteria and some chemoautotrophic bacteria. Previous studies of Halothiobacillus neapolitanus and Nitrobacter agilis carboxysomes suggest that the structures are either icosahedral or dodecahedral. To determine the protein shell structure more definitively, purified H. neapolitanus carboxysomes were re-examined by cryo-electron tomography and scanning transmission electron microscopy (STEM). Due to the limited tilt angles in the electron microscope, the tomographic reconstructions are distorted. Corrections were made in the 3D orientation searching and averaging of the computationally extracted carboxysomes to minimize the missing data effects. It was found that H. neapolitanus carboxysomes vary widely in size and mass as shown by cryo-electron tomography and STEM mass measurements, respectively. We have aligned and averaged carboxysomes in several size classes from the 3D tomographic reconstruction by methods that are not model-biased. The averages reveal icosahedral symmetry of the shell, but not of the density inside it, for all the size classes. (c) 2006 Elsevier Ltd. All rights reserved.