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首页> 外文期刊>Acta crystallographica. Section D, Structural biology. >Using cryo‐electron microscopy maps for X‐ray structure determination of homologues
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Using cryo‐electron microscopy maps for X‐ray structure determination of homologues

机译：使用低温电子显微镜地图应承担的X射线同系物的结构测定

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摘要

The combination of cryo‐electron microscopy (cryo‐EM) and X‐ray crystallography reflects an important trend in structural biology. In a previously published study, a hybrid method for the determination of X‐ray structures using initial phases provided by the corresponding parts of cryo‐EM maps was presented. However, if the target structure of X‐ray crystallography is not identical but homologous to the corresponding molecular model of the cryo‐EM map, then the decrease in the accuracy of the starting phases makes the whole process more difficult. Here, a modified hybrid method is presented to handle such cases. The whole process includes three steps: cryo‐EM map replacement, phase extension by NCS averaging and dual‐space iterative model building. When the resolution gap between the cryo‐EM and X‐ray crystallographic data is large and the sequence identity is low, an intermediate stage of model building is necessary. Six test cases have been studied with sequence identity between the corresponding molecules in the cryo‐EM and X‐ray structures ranging from 34 to 52% and with sequence similarity ranging from 86 to 91%. This hybrid method consistently produced models with reasonable R work and R free values which agree well with the previously determined X‐ray structures for all test cases, thus indicating the general applicability of the method for X‐ray structure determination of homologues using cryo‐EM maps as a starting point.
机译：结合低温电子显微镜(低温检测——EM)和X射线晶体学反映了结构生物学的重要趋势。先前发表的研究中,一种混合方法X射线结构使用应承担的决心初始阶段由相应的提供给出了部分低温EM应承担的地图。地理X射线结晶学的目标结构不相同但相应的同源低温的分子模型EM应承担的地图,然后开始阶段的准确性下降使整个过程更加困难。修改后的混合方法来处理这种情况下。步骤:低温高EM地图替换在扩展阶段通过nc平均和双空间迭代模型建筑。低温的EM和X射线晶体数据很大序列的身份低,一个中间模型构建阶段是必要的。病例研究序列的身份中相应的分子之间低温的EM和X射线结构从34和序列相似性从86年的52%到91%。模型与合理的工作和R自由的价值观以前同意的决定吗X射线结构所有测试用例,因此说明的一般适用性方法X射线结构测定同系物使用低温EM应承担的地图作为开始点。

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