Author:
Liu Yan-Ping,Tang Qun,Zhang Jie-Zhong,Tian Li-Fei,Gao Pu,Yan Xiao-Xue
Abstract
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.
Funder
National Natural Science Foundation of China
Pilot Strategic Science and Technology Projects B, Chinese Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Cited by
20 articles.
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