Structural basis underlying complex assembly and conformational transition of the type I R-M system
Structural basis underlying complex assembly and conformational transition of the type I R-M system
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I型R-M系统复杂组装和构象转变的结构基础
DOI：
10.1073/pnas.1711754114
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发表时间：
2017-10-17
影响因子：
11.1
通讯作者：
Yan, Xiao-Xue
中科院分区：
文献类型：
--
作者：
Liu, Yan-Ping;Tang, Qun;Yan, Xiao-Xue
I型限制-修饰（R-M）系统是具有单独的DNA识别（S）、甲基化（M）和限制（R）亚基的多亚基酶。尽管广泛的研究跨越五十年，亚基组装和构象转变的详细分子机制仍然不清楚，由于缺乏高分辨率的结构信息。在这里，我们报告的原子结构的I型MTase复合物（2 M +1 S）结合到DNA和辅因子S-腺苷甲硫氨酸的“开放”的形式。M和S亚基之间的分子间相互作用由四螺旋束基序介导，这也决定了相互作用的特异性。开放和以前报道的低分辨率“封闭”结构之间的结构比较确定了MTase复合物内的巨大构象变化。此外，生化结果表明，R亚基更喜欢加载到封闭形式的MTase上。基于我们的研究结果，我们提出了一个更新的模型，为复杂的装配。这里报道的工作为将来在分子生物学中的应用提供了指导。
Type I restriction-modification (R-M) systems are multisubunit enzymes with separate DNA-recognition (S), methylation (M), and restriction (R) subunits. Despite extensive studies spanning five decades, the detailed molecular mechanisms underlying subunit assembly and conformational transition are still unclear due to the lack of high-resolution structural information. Here, we report the atomic structure of a type I MTase complex (2M+1S) bound to DNA and cofactor S-adenosyl methionine in the "open" form. The intermolecular interactions between M and S subunits are mediated by a four-helix bundle motif, which also determines the specificity of the interaction. Structural comparison between open and previously reported low-resolution "closed" structures identifies the huge conformational changes within the MTase complex. Furthermore, biochemical results show that R subunits prefer to load onto the closed form MTase. Based on our results, we proposed an updated model for the complex assembly. The work reported here provides guidelines for future applications in molecular biology.